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I am interested in understanding how the global population pyramid has changed in the last couple of centuries.
I have two questions:
1) Has this been calculated? Are there estimates of population pyramids from the 19th century? Or from the beginning of 20th century? The earliest I have seen is 1950 (below).
2) If it hasn't been done, how can I construct it? It should be possible to model the population dynamics using birth and death rates (I would be surprised if this hasn't been done, as it has many applications outside of demography - e.g. economics).
World population hits 7 billion
Demographers have estimated that on 31 October 2011 world population reached the 7 billion mark, one billion more than 12 years before and 6 billion more than in 1800. Naturally this is just an estimate because the data available are not accurate enough to establish the exact moment in which world population reached 7 billion inhabitants, but it is a symbolic date that makes us face the issue of the demographic growth that has characterised the past century. The exponential growth of the world population is a recent phenomenon. About 2000 years ago about 300 million humans inhabited the Earth. It took over 1600 years to double this figure to 600 million. The world population reached the first billion in 1800 and since then, in just over two centuries, the population has increased seven-fold. As can be observed in the graph that shows the stages of world population growth (See graph on World population growth), the sharp increase in population growth began in the mid-20th century: in fact, since 1959, world population has been growing on average at about one billion people every 13 years. The post-war economies of developed countries grew steadily in time of peace and there was an acceleration of the industrialisation processes (as a result of post-war reconstruction). The swelling middle class was an indication of growing economic well-being. At the same time, the process of economic globalisation and the increased circulation of money, commodities and technology brought about a general improvement in human well-being even in developing countries. The quality of life increased correspondingly with the improvement in well-being. Thanks to the improvement in sanitary conditions, infant mortality rates have declined dramatically, passing from around 133 deaths per thousand births in the Fifties to 46 per thousand in the period between 2005 and 2010. The average life expectancy increased from around 48 years in the early 1950s to 70 in the first decade of the 21st century. Population growth can therefore be considered an achievement for mankind, even though one must keep in mind that not everyone gets an equal share of the benefits of this economic growth nor do they enjoy a better quality of life. In fact, there are still great inequalities among countries, in particular between industrialised and developing countries and even within countries.
A population pyramid is a useful instrument to evaluate how the population of a country is evolving and to compare the demographic trends that characterise different countries. The population pyramid (or age structure diagram) is a graphical illustration used in demographic statistics that portrays the age structure of a population. Usually it consists of two horizontal bar graphs (one showing the female population, the other showing the male population) placed symmetrically back-to-back around a vertical axis, that indicates the age of the population in 5-year intervals. The x-axis indicates the number of people (or the percentage) in each age group.
The shape of the age structure diagram gives information on the demographic history of a population and indicates the demographic trend. In particular, a distinctly triangular-shaped pyramid indicates a growing population, a more rectangular-shaped age pyramid indicates rates of population growth rate around zero, and a diamond-shaped structure reflects a decreasing population.
For a better understanding of the current demographic trends, let’s analyse the age structure diagrams of Japan (See graph Population pyramid of Japan in 2011) and Nigeria (See graph Population pyramid of Nigeria in 2011), two countries with different demographic profiles, i.e. one of an industrialised country the other of a developing country. Japan’s age pyramid has the typical “spinning top” shape that indicates a declining population. In fact, in Japan, which is the country with the highest life expectancy (83 years), 23% of the population is over 65 years old and only 13% is under 15. The young population (in the fertile age range) is decreasing while the elderly population is increasing.
In Nigeria, instead, a contrasting demographic situation can be found. Nigeria’s triangular-shaped population pyramid reflects a growing population: 43% of the population is under 15 years old, while only 3% is over 65. The population pyramids of Nigeria and Japan reflect a widespread demographic tendency: developed countries have an ageing population with near zero population growth, while developing countries are contributing to world population growth. The main cause of ageing of the population in developed countries is declining fertility rates, that is, the number of children that would be born to a woman in her lifetime, along with the simultaneous rising life expectancy. In fact, the average global fertility rate has more than halved from the 1950s to today, dropping from 6 to 2.5 children per woman. This decrease is due to economic growth, development and the cultural and social changes that followed. As an example, suffice it to highlight the change in women’s role in society, thanks to a greater access to education and to paid jobs. Higher fertility rates are strongly correlated to high levels of poverty and poor access for women to education.
In its World Population Prospects: The 2010 Revision, published in May 2011, the Population Division of the United Nations Department of Economic and Social Affairs, estimated that world population will amount to 9.3 billion in 2050 and over 10 billion before the end of the century. Notwithstanding an overall decrease in fertility, in fact, at least 80 million people are added every year to the world population, a number that is equivalent to approximately the inhabitants in Germany or Ethiopia. In the next few years, the population growth shall be sustained by the countries with the highest fertility rate, most of which are in Africa, followed by Asia and Latin America. Asia, in which 60% of the present world population is concentrated, remains the macro-region with the highest population density in the world, even though Africa shall advance and its population shall triple, from one billion in 2011 to 3.6 in 2100. According to the demographic projections, the growth of the Asian population should reach a peak around mid century, and will then start to decrease. Lastly the inhabitants of America, Europe and Oceania, which are currently 1.7 billion will reach almost 2 billion by 2060 and will then decrease very slowly (they will still be about 2 billion towards the end of the century).
From the countryside to the cities: the rural exodus
According to a study carried out by the UNO, in 2008, the world’s urban population was more than the rural population for the first time. Since the first half of the 20th century, the world has witnessed a rapid urbanization of the population. From 1950 to date, in little more than sixty years, the population living in the cities has multiplied five times, passing from 745 million to 3.6 billion inhabitants, the rural population instead has shown a weaker growth rate. and in the same reference period rural population only doubled. It is estimated that in 2050 the global urban population could amount to 6 billion, out of the estimated 9.3 billion. 2 people out of 3 therefore will be living in urban centres. Instead, in the estimates for 2050 for the rural population, a mild decrease in the growth is foreseen from 3.2 billion in 2010 to 3 billion in 2050. Therefore the increase in the world population will be prevalently in the urban areas. This is a completely different picture from the previous period, in which the inhabitants of the rural areas were still prevalent, even though the population growth was mainly the urban areas. The most relevant aspect of this “urban revolution” is that the future demographic growth will be absorbed almost entirely by the urban areas of the developing countries. In the urban population map (See graph Urban population map), in fact, it is possible to observe how the urban population has varied (as a percentage of the total population) in the principal geographic areas in 1950, in 2010 and future forecasts for 2050. As it can be noted in the histograms on the map, urbanization started in the industrialized countries (North America, Europe and Oceania) and has started in the developing countries only recently. At present, in fact, in Africa and in Asia the rural population is still more than the urban population, unlike in the industrialized countries where already in 1950 most of the population lived in the cities. In the future years, instead, the trends will be inverted, as it can be observed in the map. In fact the forecasts for 2050 indicate that the phenomenon of urbanization will prevalently regard the developing countries, in particular Asia and Africa, while in the industrialized countries the urban population will increase only little.
Urbanisation and megacities
The formation of megacities * is one of the most significant urbanistic phenomena of the 21st century. In 1950, only two cities had over 10 million inhabitants (Tokyo and New York). 25 years later, in 1975, with Mexico City, the number of megacities rose to three. Today the number of megacities has risen to 23. The list of megacities is headed by Tokyo, which extends 120 km on the sea, and has a population of over 37 million inhabitants. Four cities with over 20 million inhabitants follow: Delhi with 22.7 million Mexico City (22.8 million), New York (20.4) and Shanghai (20.2). These are followed by Sao Paolo in Brazil, Mumbai in India, Beijing in China, Dhaka in Bangladesh, Kolkata in India, Karachi in Pakistan, Buenos Aires in Argentina, Los Angeles-Long Beach-Santa Ana in the USA Rio de Janeiro in Brazil Manila in the Philippines Moscow in Russia Osaka-Kobe in Japan Istanbul in Turkey Lagos in Nigeria Cairo in Egypt, Guangzhou, Guangdong in China Shenzen in China and Paris in France. This process is destined to continue and to develop in the future years, with a strong impact on social and economic development. It is estimated, in fact, that by 2025 there will be 37 cities with over 10 million inhabitants. In particular, none of the metropolises, for which a rapid growth is expected in the next few years, is located in an industrialised country. In 2025, out of the 37 megacities, eight will be in the industrialized countries, (two in Japan, three in Europe, three in the USA), seven in China and six in India. Not only will there be an increase in the population, but also a redistribution of human beings around the World.
* The term «megacity», according to a definition given by the United Nations, refers to an urban agglomerate with a population of over 10 million inhabitants.
Is the Earth over-populated?
Since 1800, the world’s population has multiplied seven and a half times. Credit: Shutterstock
In 1800 the world's population was around 1 billion people. Since then it has increased more than sevenfold to reach over 7.5 billion in 2017 (see figure 1), and is forecast to top 10 billion by 2050. Will population growth inevitably continue? Will it level off over the long term? Should we try to reduce or stop this growth?
Simply put, the world's population is increasing because the number of births outnumber deaths by three to one. A surplus of births first occurred two centuries ago in Europe and North America, when mortality started to decline. This marked the beginning of what scientists call the demographic transition. This transition subsequently spread to the rest of the planet as social and economic progress, combined with advances in hygiene and medicine, began to reduce mortality rates.
Rapid population growth in Africa
Still, the annual population growth rate actually peaked half a century ago at more than 2%, and has fallen by half since then, to 1.1% in 2017 (see figure 2). This trend should continue in coming decades because fertility is decreasing at global level, from 5 children per woman in 1950 to 2.5 today. In 2017, the regions where fertility remains high (above 3 children per woman) include most countries of intertropical Africa and an area stretching from Afghanistan to northern India and Pakistan (see map below). These are the regions that will drive future world population growth.
A key trend in future decades will be population growth in Africa. Including North Africa, the continent's population could quadruple over the next century, rising from 1 billion inhabitants in 2010 to an estimated 2.5 billion in 2050 and more than 4 billion in 2100, despite the negative impact of the AIDS epidemic and other factors. While, globally speaking, one person in six currently lives in Africa, the proportion will probably be more than one in three a century from now. Growth should be especially rapid in sub-Saharan Africa, where the population may rise from just over 800 million in 2010 to 4 billion in 2100.Figure 1: World population since 1800 and projections up to 2100. Credit: Gilles Pison, based on United Nations data, CC BY
World fertility (2017), average number of children per woman
What will happen in the coming decades?
These figures are projections, and no one can predict what the future will bring. That said, demographic projections are quite reliable for forecasting population size over the next 10, 20 or 30 years. Most of the people who will be alive in 2050 have already been born, their number is known and we can estimate quite accurately the proportion among those currently alive who will die. Likewise, the women who will bear children over the next 20 years are already alive today, and can be counted. By estimating their potential fertility we can determine the number of future births with relative accuracy.
It would be unrealistic to imagine that population trends can be modified over the short term. Depopulation is not an option. Indeed, how could it possibly be achieved? Through increased mortality? No one hopes for that. Through mass emigration to Mars? Unrealistic. Through a drastic and durable decrease in fertility to below replacement level (2.1 children)? This is already taking place in many parts of the world, as couples decide to have fewer children so as to give them the best chances for a long and fulfilling life.
But for reasons of demographic inertia, this does not result in an immediate population decline. Even if world fertility were just 1.6 children per women, as is the case in Europe and China, the population would continue to increase for several more decades there are still large numbers of adults of childbearing age who were born when fertility was still high, so the number of births also remains high. The proportion of old and very old people is very small, on the other hand, so deaths are far less numerous.Figure 2: World population growth rates1700-2100. Credit: Gilles Pison, based on United Nations data, CC BY
The question of fertility decline
Demographers were taken by surprise in the 1960s and 1970s when surveys revealed the onset of a sharp decline in fertility in many countries of Asia and Latin America, and demographic projections for these regions of the world were revised strongly downward.
Another more recent surprise concerns intertropical Africa. Fertility decline in the region was expected to begin later than in Asia and Latin America because of slower social and economic development. But it was assumed that, while delayed, the transition would follow the standard pattern, with a decline similar to that observed in other regions of the Global South. This is indeed the case in North and southern Africa, but not in intertropical Africa, where the decline is occurring more slowly. This explains the upward revision of projections for Africa, a continent which could be home to more than a third of the world's population by 2100.
Fertility is in fact decreasing in intertropical Africa, but among the educated and urban populations and not in rural areas where most of the population still lives. While the fertility decline is still slower than that observed some decades ago in Asia and Latin America (see figure 4), the reason does not lie in an unwillingness to use contraception.
While most rural families have yet to adopt a two-child family model, they would prefer to have fewer children and to space them further apart. They are willing to use contraception for this purpose, but the necessary services are not available to them. National birth-control programmes exist but are ineffective because they lack resources and, above all, because their organisers and the personnel responsible for implementing them are unenthusiastic. Many are not convinced of the advantages of birth control, even at government level, even if this is not the official line adopted with respect to international organisations
This is one of the differences with respect to Asia and Latin America in the 1960s and 1970s, and one of the obstacles to faster fertility decline in sub-Saharan Africa.
Long-term outlook: explosion, implosion or equilibrium?
Beyond the next 50 years, however, the future is much more uncertain and there is no established forecasting model.
The demographic transition, which has served well to predict changes over the last two centuries, will be of little use for this distant future. There is much uncertainty about future fertility. If the small family becomes a dominant model over the long term, with mean fertility of less than two children per women, then the world population, after peaking at 10 billion, will gradually decrease to the point of extinction.
But another scenario is possible, in which fertility recovers in the countries where it is now very low, ultimately stabilising at more than two children per woman worldwide. This would result in continuous growth, and again in the extinction of the human race, this time due to overpopulation. If we cannot resign ourselves to these catastrophic scenarios of extinction through under- or over-population, then we must imagine a scenario of ultimate equilibrium.Figure 4: Fertility-rate trends by world region. Credit: Gilles Pison, based on United Nations data., CC BY
It is lifestyle that matters
Of course, humans must start thinking today about the need for long-term equilibrium, but it is the next few decades that are of most urgent concern.
The world population will inevitably increase by 2 to 3 billion between now and 2050 because of demographic inertia that no one can prevent. Nonetheless, we have the power to change yet now our way of living – and there is an urgent need to do so – by ensuring greater respect for the environment and more efficient use of natural resources. All in all, the long-term survival of humankind depends more on its choice of lifestyle than on its population size.
This article was originally published on The Conversation. Read the original article.
The Story of Sri Lanka
Prior to World War II, advances in public health has been largely limited to affluent, industrialized countries. But since then, improvements in public health have been made in many of the poorer countries of the world - always with dramatic effect on death rates.
- In 1945, the death rate in Sri Lanka (then called Ceylon) was 22/1000.
- In 1946, a large-scale program of mosquito control - using DDT - was started.
- By eliminating its vector, the incidence of malaria dropped sharply.
- After 9 years, the death rate dropped to 10/1000, and by 2012 was 6.
- But a compensating decline in birth rates has come more slowly (18/1000 in 2012).
- So by 2012 the population was increasing at an annual rate of 1.2% (12/1000/year).
- At this rate the population would double in 57.5 years.
GOVERNMENT POLICIES TO CONTROL POPULATION
In some countries, governments need to introduce policies to control their populations. Below are two contrasting policies - China's 'One Child' policy and Singapore's '3 or more' policy.
CHINA'S 'ONE CHILD' POLICY:
In the late 1970s, in an attempt to slow down the rate of population growth, the Chinese government introduced a 'One Child' policy, which stated that a couple in China could only have one child. The thinking behind the new policy was that China's population growth-rate was unsustainable. In 1950 the rate of population change in China was 1.9% each year. If this doesn't sound high, consider that a growth rate of only 3% will cause the population of a country to double in less than 24 years!
Previous Chinese governments had actually encouraged people to have a lot of children, in order to increase the country's workforce. But by the 1970s the government came to realise that current rates of population growth would soon become unsustainable.
IMPACTS OF THE POLICY:
SINGAPORE'S '3 OR MORE' POLICY:
In the 1960s Singapore had a high birth rate and a lowering death rate being in stage 2 of the DTM. The government introduced a ‘two is enough’ policy. This policy was very successful and the birth rate fell considerably to a low of nine per thousand. In the late 1980's the government realised that if the birth rate continued to fall they would not have enough workers and the economy would stop growing. So in 1987 they introduced the ‘3 or more policy’ which gave people incentives to have more children. It has not been very successful.
World population pyramid since 1800 - Biology
World Population Growth
by Max Roser and Esteban Ortiz-Ospina[cite]
First published in 2013 updated April, 2017.
200 years ago there were less than one billion humans living on earth. Today, according to UN calculations there are over 7 billion of us.1 Recent estimates suggest that today's population size is roughly equivalent to 6.5% of the total number of people ever born.2This is the most conspicuous fact about world population growth: for thousands of years, the population grew only slowly but in recent centuries, it has jumped dramatically. Between 1900 and 2000, the increase in world population was three times greater than during the entire previous history of humanity—an increase from 1.5 to 6.1 billion in just 100 years.
How the world population is changing is of great importance for humanity’s impact on the Earth’s natural environment, but it also gives reasons to hope for a good future. This is because we have a bigger team of better educated people who can contribute to the solutions that improve global well-being.
A picture of the world population in the very long-run shows extremely rapid growth. Indeed, for a long time the world population grew at an increasing rate. However, if we focus on the last couple of decades, we see that this pattern no longer holds, as the annual rate of population growth has been recently going down. 1962 saw the growth rate peak at 2.1%, and it has since fallen to almost half. A long historical period of accelerated growth has thus come to an end.
Based on these observations, world history can be divided into three periods marked by distinct trends in population growth. The first period, pre-modernity, was a very long age of very slow population growth. The second period, beginning with the onset of modernity—which was characterized by rising standards of living and improving health—had an increasing growth rate that continued to rise through 1962. Today, the second period is over, and the third period is unfolding the population growth rate is falling and will likely continue to fall, leading to an end of population growth towards the end of this century.
I. Empirical View
I.1 Population size vs. population growth rate
In order to study how the world population changes over time, it is useful to consider the rate of change rather than focusing only on the total population level. The following visualization presents the annual population growth rate superimposed over the total world population for the period 1750-2010, as well as projections up to 2100. This is the period in history when population growth changed most drastically. Before 1800, the world population growth rate was always well below 1%. Over the course of the first fifty years of the 20th century, however, annual growth increased to up to 2.1%—the highest annual growth rate in history, which was recorded in 1962. Since peaking, the growth rate has systematically been going down, with projections estimating an annual rate of 0.1% for 2100.
This means that while the world population quadrupled in the 20th century, it will not double in the 21st century.
World population, 1750-2015 and projections until 21003
I.2 Long-run historical perspective
World Population from 10,000 BCE to 2100 CE
The chart below shows the the increasing number of people living on our planet over the last 12,000 years. A mind boggling change: The world population today that is 1,860-times the size of what it was 12 millennia ago when the world population was around 4 million or half of the current population of London.
What is striking about this chart is of course that almost the entire action happened just very recently. Historical demographers estimate that around the year 1800 the world population was only around 1 billion people. This implies that on average the population grew very slowly over this long time from 10,000 BCE to 1700 (by 0.04% annually).
After 1800 this changed fundamentally: The world population was around 1 billion in the year 1800 and increased 7-fold since then.
Around 108 billion people have ever lived on our planet. This means that today's population size makes up 6.5% of the total number of people ever born.4
The visualization allows you to add the UN's projected population increase through the end of the 21st century as estimated in their Medium Variant (for more detail on the UN's population estimates, see below). Hovering your mouse over the plotted line will show you population figures for each year.
For the long period from the appearance of modern Homo sapiens up to the starting point of this chart in 10,000 BCE it is estimated that the total world population was often well under one million.5 In this period our species was often seriously threatened by extinction.6
World Population over the last 12,000 years and UN projection until 210010000 BCE8000 BCE6000 BCE4000 BCE2000 BCE0210002 billion4 billion6 billion8 billion10 billion LINEAR
Source: World Population over 12000 years - various sources (2016), Medium Projection – UN Population Division (2015 revision)
The visualisation below presents a different perspective on the long-term increase of the world population and asks how long it took for the world population to double.
The visualisation shows how strongly the growth rate of the world population changed over time: In the past the population grew slowly: it took nearly seven centuries for the population to double from 0.25 billion (in the early 9th century) to 0.5 billion in the middle of the 16th century. As the growth rate slowly climbed, the population doubling time fell but remained in the order of centuries into the first half of the 20th century. Things sped up considerably in the middle of the 20th century. The fastest doubling of the world population happened between 1950 and 1987: a doubling from 2.5 to 5 billion people in just 37 years — the population doubled within a little more than one generation. This period was marked by a peak population growth of 2.1% in 1962.
Since then, population growth has been slowing, and along with it the doubling time. In this visualisation we have used the UN projections to show how the doubling time is projected to change until the end of this century. By 2088, it will once again have taken nearly 100 years for the population to double to a predicted 11 billion.
Time it took for the world population to double7
Time taken for population to increase by one billion
The visualisation below provides an additional perspective on population growth: the number of years it took to add one billion to the global population. Also shown in this figure is the number of years projected up to 11 billion based on the UN's 'medium variant' projection.
This visualisation shows again how the population growth rate has changed dramatically through time. It wasn't until 1803 that the world reached its first billion it then took another 124 years to reach two billion. By the third billion, this period had reduced to 33 years, reduced further to 15 years to reach four. The period of fastest growth occurred through 1975 to 2011, taking only 12 years to increase by one billion for the 5th, 6th and 7th.
The world has now surpassed this peak rate of growth, and the period between each billion is expected to continue to rise. It's estimated to take approximately 13 years to reach eight billion in 2024 a further 14 years to reach 9 billion in 2038 18 years to reach 10 billion in 2056 and a further 29 years to reach the 11th billion in 2088.
Time it took for the world population to increase by one billion8
I.3 Country trends over the last centuries
The global pattern masks a great deal of heterogeneity across countries faster population growth started at different points in time in each country. The following visualization shows total population by country in the last centuries.
The data below shows the latest UN data for the time since 1950 and the estimates published by Gapminder for the period before.
Data from Clio-Infra on the population by country over the last 500 years can be seen in this chart. Substantial differences are evident here: adding the U.S. to the graph reveals that, while the population in France roughly doubled in the period 1800-2000, in this same period the population in the U.S. increased almost 50-fold.
This also meant that the population density increased rapidly in many countries, as can be seen on this interactive visualization.
Population by country17001750180018501900195020160200 million400 million600 million800 million1 billion1.2 billion1.4 billionChinaIndiaUnited StatesBrazilSource: Gapminder until 1949, UN Population Division from 1950-
I.4 Shares by world regions
The estimates provided by the History Database of the Global Environment (HYDE) are shown in the following visualization that provides a break down of the world population by world regions.
Asia is – and has been for a long time – the most populous region in the world.
World population by world regions18201850190019502000201601 billion2 billion3 billion4 billion5 billion6 billion7 billionNorth and CentralAmericaSouth AmericaOceaniaEuropeAsiaAfricaSource: Global Population by Region - HYDE (2016)
I.5 Recent history and projections
In terms of recent developments, the data from the UN Population Division provides consistent and comparable estimates (and projections) within and across countries and time, over the last century. This data starts from estimates for 1950, and is updated periodically to reflect changes in fertility, mortality and international migration (for more information see the Data Quality section at the end of this entry).
The global population growth rate peaked long ago
The chart below shows that global population growth reached a peak in 1962 and 1963 with an annual growth rate of 2.2% but since then, world population growth was halved.
For the last half-century we have lived in a world in which the population growth rate has been declining. The UN projects that this decline will continue in the coming decades.
The absolute increase of the population per year has peaked in the late 1980s at over 90 million additional people each year and can be seen here.
Natural population growth
'Natural population growth' measures the rate of population increase as determined solely by births and deaths. Migration flows are not taken into account.
The map below illustrates the rate of natural population growth by country from 1955 to 2015 (use the slider underneath the map to change years).
We see that there are some countries today where the natural population growth is slightly negative: the number of deaths exceed the number of births. When we move the time slider underneath the map to past years, we see that this is a new phenomenon. Up until the 1970s, there were no countries with a negative natural population growth.
Worldwide, population growth is slowing—you can press the play arrow at the bottom of the chart to see the change over time.
Natural population growth, 2015Natural population growth is the population increase determined by births and deaths. Migration flows are not takeninto account.No data
1Population growth by country
The following visualization presents the rate of population growth by country—and here, migration flows are taken into account in addition to the population growth determined by births and deaths. The chart shows data for the period 1955-2015, plus projections for 2015-2100 using the UN Population Division data.
You can toggle the visualization from chart to map view for a wider, cross-country comparison. As you can see, growth rates in most countries have been going down since the 1960s. Yet substantial differences exist across countries and regions. While Western Europe's growth rates are currently close to zero, sub-Saharan Africa's rates remain higher than 3%—that is, still higher than the peak growth rates recorded for the world at the beginning of the 1960s. Moreover, in many cases there has been divergence in growth rates. For instance, while India and Nigeria had similar growth rates in 1960 (around 1.7%), they took very different paths in the following years and thus currently have populations that grow at very different rates (about 1.26% for India compared to 2.67% for Nigeria).
Population growth rate, 2015Average annual rate of population change (including the UN's 'Medium variant' projections until 2100)No data 6%Source: UN Population Division (2017 Revision)
Population growth by the level of development
The following visualization presents how the population growth rate has changed for 'more developed', 'less developed' and 'least developed' countries (UN categorization), and how they are projected to change through 2100 (UN Population Division estimates and projections from the 2015 revision).
Developed countries reached the fastest growth rates longer ago and the population growth rates there have been falling for many decades. The less developed countries' growth rate peaked in the late 1960s and in the least developed countries the population growth rate peaked around 1990.
Over the last two decades we are seeing declining population growth rates in countries at all stages of development.
Population growth rate by world region, 1955-2015 and projections through2100Projections use the UN medium variant195019802000202020402060208020990%0.5%1%1.5%2%2.5%More developed regions - Projectedgrowth rateLess developed regions - Projectedgrowth rateLeast developed countries - Projectedgrowth rateSource: UN Population Division (2017 Revision)Note: More developed regions comprise Europe, Northern America, Australia/New Zealand and Japan less developed regions comprise all regionsof Africa, Asia (excluding Japan), Latin America and the Caribbean plus Melanesia, Micronesia and Polynesia least developed countries are 48countries, 33 in Africa, 9 in Asia, 5 in Oceania plus one in Latin America and the Caribbean.
The above discussion also shows that there are interesting patterns of population density: the most densely populated regions today have also been the most densely populated regions throughout modern history. India is a prime example of this. The following visualization shows population density patterns by country using data from the History Database of the Global Environment (HYDE). Switch to the map view for a global perspective.
Population densityNumber of inhabitants per square kilometer.5000 BCE4000 BCE3000 BCE2000 BCE1000 BCE010002100050100150200 LINEAR
Population projections based on education levels
The International Institute for Applied Systems Analysis (IIASA) is an interdisciplinary, highly-respected research institution near Vienna, Austria. The IIASA population projections are the most cited alternative to the UN work.
Interestingly, their medium projection for population growth (which they consider most likely) stands in stark contrast to the UN projection. While the medium variant of the UN projection sees the world population growing continuously throughout the 21st century, the IIASA medium scenario sees the world population increase to 9.4 billion in 2070, and then begin a slow decline to reach below 9 billion by the end of the century.
As the IIASA researchers explain, there are important methodological differencesbetween the UN and IIASA projections. The UN uses probabilistic population projections to extrapolate populations for each country over the 21st century and applies the same statistical methodology to all countries. In contrast, the IIASA researchers have a country-specific approach that takes into account the knowledge of experts for each country separately.
The other important feature of the IIASA projection is that it takes into account how educated a given population is. As we show below, there is a strong link between education and fertility—more educated women have fewer children. This link is factored into IIASA's model and contributes to their projection of a much smaller total world population over the course of the 21st century.
Breaking down the population by education level is especially interesting: we see that our world will be inhabited by more and more educated people. The visualization below shows that in 1970 there were only around 700 million people in the world who had secondary or post-secondary education. By the end of this century, the number of people with secondary or post-secondary education will have increased 10-fold and will reach 7 billion people (a figure similar to the entire current world population)!
The projection also shows that the number of people with no education will decrease continuously and that by the end of this century virtually all people in the world will have received some level of education.
Projected world population by level of educationThis visualization shows the Medium projection by the International Institute for Applied Systems Analysis (IIASA). Theresearchers who created this projection describe it as their "middle of the road scenario that can also be seen as themost likely path".1970198020002020204020602080210002 billion4 billion6 billion8 billionPost SecondaryUpper SecondaryLower SecondaryPrimaryIncomplete PrimaryNo EducationUnder 15Source: Global Projection, Medium SSP2 - IIASA (2016)
I.6 How will the global demography change?
At times when the population pyramid actually resembles a pyramid people are facing the risk to die at any point in their life. The uniform narrowing of the pyramid to the top is evidence of the continuous risk of death from birth on and through all ages. The visualisation here shows this was still the global reality in 1950 – the narrowing of the pyramid just above base is testimony to the fact that in 1950 every fourth child diedbefore it reached the age of five. The continuing narrowing to the top shows the high mortality throughout all ages.
At a time when the top of the pyramid is much wider and the pyramid increasingly resembles a box shape, the population lives through young ages with very low risk of death and dies at an old age. The box shape is the demographic structure of a healthy population. The projection in the visualisation shows that the global demography changes from the pyramid to the box shape – the world population through all ages is becoming increasingly healthier.
In addition to mortality it is also fertility that shapes the form of the demographic structure. The first aspect that matters for the number of new births in a population is the fertility rate, the number of births per woman in the reproductive age. But if there are only few women in reproductive age the number of births will be low even with a high fertility rate. Therefore the age structure of women in a population matters too – specifically it is the share of women in the reproductive age that determines the number of births. A bulge of women in this age keeps the number of birth high even when fertility is already low, this is what demographers refer to as ‘population momentum’. The pyramid for 2016 shows that the largest cohort of women today are the very young women. The last decades of population growth have left us with a bulge of population in the childbearing ages. For this reason the world population will continue to increase, even as the fertility rate of the world is falling to the replacement level fertility.
The World Population Pyramid in 1950, 2017 and 21009
The world is reaching peak children
A second aspect to note regarding the age structure of the world population is how the very young population will change. Here we can see that at the end of the century the base of the structure is narrower than today. There will be fewer children born at the end of this century than today.
The world is approaching what the late Hans Rosling called “the age of peak child”. The solid purple line in the visualisation below indicates the total population of people under the age of 5, and the dotted purple line shows projections for this age group through 2100. As we can see, we are not far away from the largest cohort of children that there will likely ever be. The gray lines show the total world population – we expect an end to population growth as the number of children in the world begins to decrease.
This is an extraordinary moment in global history. In the past only two children per woman reached adulthood – if more had survived the population size would have not been stable. This also means that the extended family with many children, that we often associate with the past, was only a reality for glimpse in time. Only the few generations during the population boom lived in families with many children – before and after two children are the norm. The future will resemble our past, except that the children are not dying, but are never born in the first place.
Between 1950 and today it was mostly a widening of the entire pyramid that was responsible for the increase of the world population. What is responsible for the increase of the world population from now on is not a widening of the the base, but a fill up of the population above the base. Not children will be added to the world population, but people in working age and old age.
At a country level “peak child” is followed by a time in which the country benefits from a “demographic dividend”. The demographic structure of a country is reshaped so that the proportion of people in working age rises and that of the dependent young generation falls. The demographic dividend can result in a rise of productive contributions and a growing economy.10 Now there is reason to expect that the world as a whole benefits from a "demographic dividend".
The big demographic transition that the world entered more than a century ago is coming to an end: Global population growth has peaked half a century ago, the number of babies is reaching its peak, and the age profile of the women in the world is changing so that ‘population momentum’ is slowly losing its momentum. This is not to say that feeding and supporting a still rising world population will be easy, but we are certainly on the way to a new balance where it is not like in our long past when high mortality kept population growth in check, but when it is low fertility that will keep the world population from growing.
World population and projected growth to 2100 (total population and underage 5)Projections are based on UN median estimates. The two series correspond to total population and population under age 5.1950198020002020204020602080210002 billion4 billion6 billion8 billion10 billionProjected total populationProjected population under age 5Source: UN Population Division (2015 Revision)
II. Correlates, Determinants & Consequences
Population growth is driven by three demographic components: fertility, mortality, and migration. In this section we delve into the drivers of population growth and begin with the widely used model to describe the observed pattern of change — the demographic transition.
II.1 Births and deaths
Population growth results from the difference between births and deaths – the two visualizations below show how these two aspects have changed since 1950.
The difference gives us the global population growth in absolute numbers: Every year 141 million are born and 57 million die – this means that we are adding 84.21 million to the world population every year.
Annual number of births by world region19501960197019801990200020102015020 million40 million60 million80 million100 million120 million140 millionAfricaAsiaLatin America andthe CaribbeanNorthern AmericaEuropeOceaniaSource: UN Population Division (2017 Revision)
Annual number of deaths by world region19501960197019801990200020102015010 million20 million30 million40 million50 millionAfricaLatin America andthe CaribbeanNorthern AmericaEuropeOceaniaAsiaSource: UN Population Division (2017 Revision)
II.2 Demographic transition
In the entry on how health has changed over the long run we show the dramatic decline of mortality that the world has seen. And in the entry on fertility we show how socio-economic changes over the course of modernization – a decline of child mortality, structural changes to the economy, and a rise of the status and opportunities for women – all contribute to a very substantial reduction of fertility.
But this alone would not explain why the size of the population increases. What is missing from the picture is the timing at which mortality and fertility changes.
The model in which this information comes together is called the ‘demographic transition’. It is shown in the schematic figure. The model explains the changing size of the total population as driven by the birth and the death rate of the population. It is a beautiful simple model that describes the pattern that we observe in countries around the world and is one of the great insights of demography.11
The five stages of the transition are described below and are illustrated in the graph that follows:
Stage 1: In the long time before modern population growth the birth rate is high, but since the death rate is also high we observe no population growth. This describes the reality through most of our history. Societies around the world remained in stage 1 for millennia.
Stage 2: Then in the second phase the health slowly starts to improve and the death rate is dropping. Since the health of the population has already improved, but fertility still remains as high as before, this is the stage of the transition at which the population increases rapidly. Families do not yet adapt their fertility to the low mortality and have many children.
Historically it is the exceptional time at which the extended family with many children is common.
Stage 3: This is when fertility declines as a result of the social changes: Parents realise that as progress kick in the mortality of children is not as high as it once was and they therefore opt for fewer births, the economy is undergoing structural changes that makes children less economically valuable, and women are empowered socially and within partnerships. The fertility rate is declining steeply.
Stage 4: The population growth comes to an end and in stage 4 as the birth rate catches up with the low mortality rate.
Stage 5: The demographic transition describes changes over the course of socio-economic modernization. What happens at a very high level of development is still not a settled question since only few societies have reached this stage. But we do have some good evidence – which we review in the entry on fertility here – that at very high levels of development fertility is rising again. Not to the very levels of the pre-modern times, but to a fertility rate around 2. As a consequence of this the natural population growth rate will be at 0% or possibly slightly above.
The five stages of demographic transition
Empirical perspective on the demographic transition
If fertility fell in lockstep with mortality we would not have seen an increase in the population at all. The demographic transition works through the asynchronous timing of the two fundamental demographic changes: The decline of the death rate is followed by the decline of birth rates.
This decline of the death rate followed by a decline of the birth rate is something we observe with great regularity and independent of the culture or religion of the population.
The chart below presents the empirical evidence for the demographic transition for five very different countries in Europe, Latin America, Africa, and Asia. In all countries we observed the pattern of the demographic transition, first a decline of mortality that starts the population boom and then a decline of fertility which brings the population boom to an end. The population boom is a temporary event.
In the past the size of the population was stagnant because of high mortality, now country after country is moving into a world in which the population is stagnant because of low fertility.
Demographic transition in 5 countries, 1820-201012
England and Wales's demographic transition
Perhaps the longest available view of the demographic transition comes from data for England and Wales. In 1981, Anthony Wrigley and Roger Schofield13 published a major research project analyzing English parish registers—a unique source that allowed them to trace demographic changes for the three centuries prior to state records. According to the researchers, "England is exceptionally fortunate in having several thousand parish registers that begin before 1600" collectively, with their early start and breadth of coverage, these registers form an excellent resource. As far as we know, there is no comparable data for any other country up until the mid-eighteenth century (see the following section for Sweden, where recordkeeping began in 1749).
The chart below shows the birth and death rates in England and Wales over the span of nearly 500 years. It stitches together Wrigley and Schofield's data for the years 1541-1861 with two other sources up to 2015 (click on the chart's 'sources' tab for details). As we can see, a growing gap opens up between the birth and death rate after 1750, creating a population explosion. Around the 1870's, we begin to see the third stage of the demographic transition. As the birth rate starts to follow the death rate's decline, that gap between the two starts to shrink, slowing down the population growth rate.
The Demographic Transition, England and WalesBirth and death rate are expressed per 1,000 of the population1541160017001800190020150510152025303540Crude Birth RateCrude Death RateSource: Our World In Data based on Wrigley and Schofield (1981), Mitchell (2010), and UK ONS (2016)Note: Death rate excludes military losses in 1915-1919 1939-1946
Sweden's demographic transition
Zooming in on one of these countries, we take a look at Sweden’s demographic transition. The country's long history of population recordkeeping—starting in 1749 with their original statistical office, ‘the Tabellverket’ (Office of Tables)—makes it a particularly interesting case study of the mechanisms driving population change.
Statistics Sweden, the successor of the Tabellverket, publishes data on both deaths and births since recordkeeping began more than 250 years ago. These records suggest that around the year 1800, the Swedish death rate started falling, mainly due to improvements in health and living standards, especially for children.14 Yet while death rates were falling, birth rates remained at a constant pre-modern level until the 1860s. During this period and up until the first half of the 20th century, there was a sustained gap between the frequency of deaths and the frequency of births. It was because of this gap that the Swedish population increased. The following visualization supports these observations.
The Demographic Transition: Decline of the death rate followed by a decline ofthe birth rateBoth the birth and death rate are expressed per 1,000 of the population17491800185019001950201001020304050Sweden - Birth RateSweden - Death RateSource: Brian Mitchell - International Historical Statistics
Changes to birth and death rate over time around the world
The visualization presents the birth and death rate for all countries of the world over the last 5 decades. You can see the change over by moving the slider underneath back and forth or by pressing the "play" button. Countries per continent can also be highlighted by hovering and clicking on them in the legend on the right side of the chart.
By visualising this change we see how in country after country the death rate fell and the birth rate followed – countries moved to left-hand-side first and then fell to the bottom left corner.
Today, different countries straddle different stages of the model. Most developed countries have reached stage four and have low birth and death rates, while developing countries continue to make their way through the stages.
Birth rate vs Death rate, 2015Both the birth and death rate are given per 1,000 people of the country's population.Deaths per 1,0002468101214Births per 1,000010203040ChinaIndiaUnited StatesBrazilPakistanNigeriaBangladeshRussiaJapanVietnamEthiopiaEgyptGermanyIranDemocratic Republic of CongoThailandSouth AfricaTanzaniaMyanmarSouth KoreaSpainUkraineKenyaAlgeriaIraqSaudi ArabiaGhanaMadagascarCote d'IvoireCameroonAngolaBurkina FasoChileNigerCambodiaZimbabweBelgiumGuineaHaitiSerbiaUnited Arab EmiratesTajikistanJordanCentral African RepublicCroatiaCongoLebanonGeorgiaKuwaitJamaicaLesothoGambiaGabonBahrainCyprusFijiVanuatuGreenlandMonacoTimorPalestineAfricaAsiaEuropeNorth AmericaOceaniaSouth AmericaSource: World Bank – WDI
Search Average annual change
II.3 Fertility and population growth
All countries in the world have moved so far into the demographic transition that high mortality is now associated with higher rather than lower population growth. It is therefore the changing fertility that is determining what happens to population growth.
The below visualization shows the rate of fertility using data from the UN Population Division. Since the 1970s fertility rates in the less developed regions of the world are falling rapidly began to converge. As we see in the projection, the demographers from the UN predict this convergence to continue over the course of this century.
In the entry on fertility, we explain what is behind lower fertility rates — lower child mortality, higher incomes, the education of women, and the availability of contraception.
The total fertility rate by development level including the UN projectionsthrough 2100Total Fertility Rate is defined as the average number of children that would be born to a woman over her lifetime if the woman wereto experience the exact current age-specific fertility rates, and the woman were to survive from birth to the end of her reproductivelife.195019802000202020402060208020990123456Least developed countries - Mediumfertility variantLess developed regions - Mediumfertility variantWorld - Medium fertility variantMore developed regions - Mediumfertility variantSource: UN Population Division (2017 Revision)Note: More developed regions comprise Europe, Northern America, Australia/New Zealand and Japan less developed regions comprise all regionsof Africa, Asia (excluding Japan), Latin America and the Caribbean plus Melanesia, Micronesia and Polynesia least developed countries are 48countries, 33 in Africa, 9 in Asia, 5 in Oceania plus one in Latin America and the Caribbean.
Children per woman vs population growth, 2015The rate of natural population increase is the population increase determined by births and deaths. Migration flows arenot taken into account.Children per woman234567Annual Rate of Natural Population Increase0%1%2%3%ChinaIndiaUnited StatesPakistanNigeriaRussiaJapanPhilippinesVietnamEthiopiaIranDemocratic Republic of CongoThailandFranceSouth AfricaColombiaSpainUkraineKenyaAlgeriaIraqAfghanistanGhanaMozambiqueCote d'IvoireBurkina FasoNigerMalawiBelgiumSomaliaIsraelBulgariaTajikistanSierra LeoneKuwaitBelizeSamoaTongaNorthern AfricaAfricaAsiaEuropeNorth AmericaOceaniaSouth AmericaSource: UN Population Division (2017 Revision)
II.4 Child mortality and population growth
In the below visualization, we can see the observed correlation between population growth and child mortality across the world. Countries with high child mortality rates tend to have faster growing populations, while countries with low child mortality rates experience lower population growth rates.
Population growth rate vs Child mortality rate, 2015The child mortality rate measures the share of children that are born alive and die before they are five years old. Therate of natural population increase is determined by births and deaths only and migration flows are not taken intoaccount.Child mortality rate0%2%4%6%8%10%12% LINEARAnnual Rate of Natural Population Increase0%1%2%3%
ChinaIndiaUnited StatesIndonesiaPakistanNigeriaRussiaJapanPhilippinesEthiopiaEgyptIranTurkeyDemocratic Republic of CongoThailandSouth AfricaTanzaniaUkraineKenyaAlgeriaIraqAfghanistanMoroccoGhanaMozambiqueSyriaCote d'IvoireCameroonBurkina FasoNigerMaliMalawiSenegalChadSouth SudanBoliviaIsraelBulgariaTajikistanLaosSierra LeoneIrelandCongoPanamaOmanNamibiaGabonTrinidad and TobagoSwazilandDjiboutiReunionBruneiMayotteAsiaPalestineSerbia (including Kosovo)AfricaAsiaEuropeNorth AmericaOceaniaSouth AmericaSource: UN Population Division (2017 Revision)
1III. Data Quality & Measurement
III.1 Data on the population of the ancient world
Kremer (1993) provides estimates of the total world population over the last 1 million years.15 He puts together UN estimates for the period 1920-1990, as well as estimates from McEvedy and Jones (1978)16 for the period 10,000 BCE-1900 CE, and Deevey (1960)17 for the period 1,000,000 BCE-10,000 BCE.
The estimates from McEvedy and Jones (1978) after 200 BCE were obtained by aggregating population estimates for individual geographic regions taken from other authors (see references therein), and these in turn were based primarily on historical sources such as Roman and Chinese censuses. Their estimates of population prior to 200BCE were based on archaeological and anthropological evidence.
Many studies not considered in Kremer (1993) provide competing estimates of world population over long historical periods (Kremer (1993) mentions Clark (1977)18 and Durand (1977)19, but there are more). The following two graphs provide a sense of the dispersion of different estimates. All long-run estimates appear to be fairly close.
Comparison of different estimates of world population for the last million years - Figure 1 in DeLong (1998)20
Total World Population – Comparison of different sourcesThis chart compares estimates of the world population published by different sources.10000 BCE8000 BCE6000 BCE4000 BCE2000 BCE019700500 million1 billion1.5 billion2 billion2.5 billion3 billion3.5 billionTuve (1976)McEvedy and Jones (1978)Durand (1974), upperDurand (1974), lowerThomlinson (1975), upperSource: World Population over 12000 years - various sources (2016)
III.2 Data quality of recent world population estimates
The most discussed estimates of world population from the last century are those from the UN Population Division. These estimates are revised periodically and aim to be consistent and comparable within and across countries and time.
The methodology used by the UN to produce their estimates and projections is explained extensively in the World Population Prospects' Methodology Report.
In short, estimates of the population in the past (i.e. 1950-2015) are produced by starting with a base population for 1 July 1950 and computing subsequent populations based on the components that drive population change (fertility, mortality, and international migration). The estimates of these components are taken directly from national statistical sources or—where only partial or poor-quality data exists—are estimated by the Population Division staff. Population counts from periodic censuses are used as benchmarks. This calculation is called the "cohort-component" method because it estimates the change in population by age and sex (cohort) on the basis of the three afore-mentioned demographic components (component): fertility, mortality, and international migration.
The process of 'revising' the estimates involves incorporating new information about the demography of each country. The following diagram explains the process used to ensure consistency.
Process for generating UN population revisions – Table I.4. in the UN World Population Prospects Methodology Report21
One of the main implications of using the cohort-component method is that it sometimes leads to marked inconsistencies with official country statistics. The following map, which shows the coverage of births through civil registration, speaks to this issue: many countries, particularly those in the least developed regions of the world, have limited census data. For countries with no data in one or two decades before each revision, the UN derives estimates by extrapolating trends from countries in the same region with a socio-economic profile considered close to the country in question.
Completeness of birth registration, 2015Completeness of birth registration is the percentage of children under age 5 whose births were registered at the time ofthe survey. The numerator of completeness of birth registration includes children whose birth certificate was seen bythe interviewer or whose mother or caretaker says the birth has been registered.No data0%10%20%30%40%50%60%70%80%90%100%Source: World Bank –
For the completeness of death reporting, see here.
Uncertainty and data quality of related measures
The track record of projections of population growth is discussed in the entry on 'Future Population Growth' here.
IV. Data Sources
IV.1 Estimates of ancient population
As discussed in the previous section, there are a number of studies providing historic population data. The most commonly cited source is McEvedy and Jones (1978).
McEvedy and Jones (1978)
Data Source: McEvedy, Colin and Richard Jones (1978), "Atlas of World Population History," Facts on File, New York, pp. 342-351 relying on archeological and anthropological evidence, as well as historical documents such as Roman and Chinese censuses
Description of available measures: Population
Time span: 400BCE-2,000CE
Geographical coverage: Global by country and regions
Impact of polygamy
Figure 5. Effects of polygamy (polygyny) compared to the baseline (figure 4). Results are the average of 1,000 model runs at each parameter setting (error bars omitted). The impact of polygamy was noticeable but not very strong. Most model runs experienced a boost of approximately 4% over baseline (i.e. 104% the growth rate of a non-polygamous population with the same parameter settings). Near the edge of population survivability (i.e. with high CBA and large gaps between children) polygyny enabled some populations to experience more growth, on average, due to the fact that unwed women were more rare. Click for larger view.
In Figure 5 we show the effect of polygamy (polygyny). A small percentage of men were allowed up to a maximum of five wives (details in Methods). On average, most model runs experienced a boost of approximately 4% over baseline (i.e. they were growing at 104% the rate of a non-polygamous model with the same parameter settings).
Near the edge of population survivability, polygyny enabled some populations to experience more growth, on average, due to the fact that unwed women were more rare. In other model runs (data not shown) we increased the polygamy rate up to 10%. At these extreme values, there was a much stronger effect at the margins of survivability, but this levelled off at higher growth rates. For most parameter settings, the net effect was not more than an additional 1% increase over baseline.
Growth of the World's Population
Today, almost 7 billion people live on our earth. Each year, the world&rsquos population grows by about 80 million. If it continues to grow at such a rate the world&rsquos population will reach 9 billion by the year 2035.
World Population from the Beginnings to the Present
Human beings have been living on earth for over a million years, but for a long time there were not very many of them. The world&rsquos population was never higher than 10 million. People died quickly because they didn&rsquot have enough food to eat. Early inhabitants were mostly hunters and fishers. Some of them gathered berries from wild plants. After people started growing crops and raising animals they had more food and lived longer.
When Jesus Christ was born about 2,000 years ago about 300 million people inhabited the earth. During the next 1500 years the population of the world grew very slowly. Many people died of illnesses and plagues . The Black Death , which sailors brought to Europe from Asia, killed about a third of the European population in the Middle Ages.
The Industrial Revolution , which began in the middle of the 18th century, started a period of rapid population growth , especially in Europe. Farmers were able to grow more and more food because they had machines to work with. New kinds of medicine helped to fight off many diseases that had killed millions of people in the centuries before. Humans also lived longer because they had cleaner drinking water.
Development of the world's population
Birth rates started to go up because families had many children. More babies than ever before survived the first few years of childhood . The one billion mark was reached in the early 1800s. In the next one hundred years the population doubled to 2 billion, and in 1960 there were 3 billion people living on earth.
The second half of the 20th century brought along some change :
- In Europe , North America, Japan and Australia the birth rate dropped because families wanted to have fewer children. Population growth in these areas slowed down .
- In the developing countries of Asia and Africa birth rates stayed high and better medical help in these regions lowered the death rates. That is why these countries are growing very rapidly .
In the last 30 years the world&rsquos population has doubled. The fastest growing region , Africa, has a growth rate of 2.8 %, the slowest growing region, Europe, about 0.3 %. On average, the world&rsquos population is growing at a rate of 1.5 % per year.
The Growth of World Population: Analysis of the Problems and Recommendations for Research and Training (1963)
THE GROWTH OF WORLD POPULATION
The population of the world, now somewhat in excess of three billion persons, is growing at about two per cent a year, or faster than at any other period in man&rsquos history. While there has been a steady increase of population growth during the past two or three centuries, it has been especially rapid during the past 20 years. To appreciate the pace of population growth we should recall that world population doubled in about 1,700 years from the time of Christ until the middle of the 17th century it doubled again in about 200 years, doubled again in less than 100, and, if the current rate of population increase were to remain constant, would double every 35 years. Moreover, this rate is still increasing.
To be sure, the rate of increase cannot continue to grow much further. Even if the death rate were to fall to zero, at the present level of human reproduction the growth rate would not be much in excess of three and one-half per cent per year, and the time required for world population to double would not fall much below 20 years.
Although the current two per cent a year does not sound like an extraordinary rate of increase, a few simple calculations demonstrate that such a rate of increase in human population could not possibly continue for more than a few hundred years. Had this rate existed from the time of Christ to now, the world population would have increased in this period by a factor of about 7×10 16 in other words, there would be about 20 million individuals in place of each
person now alive, or 100 people to each square foot. If the present world population should continue to increase at its present rate of two per cent per year, then, within two centuries, there will be more than 150 billion people. Calculations of this sort demonstrate without question not only that the current continued increase in the rate of population growth must cease but also that this rate must decline again. There can be no doubt concerning this long-term prognosis: Either the birth rate of the world must come down or the death rate must go back up.
POPULATION GROWTH IN DIFFERENT PARTS OF THE WORLD
The rates of population growth are not the same, of course, in all parts of the world. Among the industrialized countries, Japan and most of the countries of Europe are now growing relatively slowly&mdashdoubling their populations in 50 to 100 years. Another group of industrialized countries&mdashthe United States, the Soviet Union, Australia, New Zealand, Canada, and Argentina&mdashare doubling their populations in 30 to 40 years, approximately the world average. The pre-industrial, low-income, and less-developed areas of the world, with two thirds of the world&rsquos population&mdashincluding Asia (except Japan and the Asiatic part of the Soviet Union), the southwestern Pacific islands (principally the Philippines and Indonesia), Africa (with the exception of European minorities), the Caribbean Islands, and Latin America (with the exception of Argentina and Uruguay)&mdashare growing at rates ranging from moderate to very fast. Annual growth rates in all these areas range from one and one-half to three and one-half per cent, doubling in 20 to 40 years.
The rates of population growth of the various countries of the world are, with few exceptions, simply the differences between their birth rates and death rates. International migration is a negligible factor in rates of growth today. Thus, one can understand the varying rates of population growth of different parts of the world by understanding what underlies their respective birth and death rates.
THE REDUCTION OF FERTILITY AND MORTALITY IN WESTERN EUROPE SINCE 1800
A brief, over-simplified history of the course of birth and death rates in western Europe since about 1800 not only provides a frame of reference for understanding the current birth and death rates in Europe, but also casts some light on the present situation and prospects in other parts of the world. A simplified picture of the population history of a typical western European country is shown in
Figure 1. Schematic presentation of birth and death rates in western Europe after 1800. (The time span varies roughly from 75 to 150 years.)
Figure 1. The jagged interval in the early death rate and the recent birth rate is intended to indicate that all the rates are subject to substantial annual variation. The birth rate in 1800 was about 35 per 1,000 population and the average number of children ever born to women reaching age 45 was about five. The death rate in 1800 averaged 25 to 30 per 1,000 population although, as indicated, it was subject to variation because of episodic plagues, epidemics, and crop failures. The average expectation of life at birth was 35 years or less. The current birth rate in western European countries is 14 to 20 per 1,000 population with an average of two to three children born to a woman by the end of childbearing. The death rate is 7 to 11 per 1,000 population per year, and the expectation of life at birth is about 70 years. The death rate declined, starting in the late 18th or early 19th century, partly because of better transport and communication, wider markets, and greater productivity, but more directly because of the development of sanitation and, later, modern medicine. These developments, part of the changes in the whole complex of modern civilization, involved scientific and technological advances in many areas, specifically in public health, medicine, agriculture, and industry. The immediate cause of the decline in the birth rate was the increased deliberate control of fertility within marriage. The only important exception to this statement relates to Ireland, where the decline in the birth rate was brought about by an increase of several years in the age at marriage combined with an increase of 10 to 15 per cent in the proportion of people remaining single. The average age at marriage rose to 28 and more than a fourth of Irish women remained unmarried at age 45. In other countries, however, such social changes have had either insignificant or favorable effects on the birth rate. In these countries&mdashEngland, Wales, Scotland, Scandinavia, the Low Countries, Germany, Switzerland, Austria, and France&mdashthe birth rate went down because of the practice of contraception among married couples. It is certain that there was no decline in the reproductive capacity in fact, with improved health, the contrary is likely.
Only a minor fraction of the decline in western European fertility can be ascribed to the invention of modern techniques of contraception. In the first place, very substantial declines in some European countries antedated the invention and mass manufacture of contraceptive devices. Second, we know from surveys that as recently as just
before World War II more than half of the couples in Great Britain practicing birth control were practicing withdrawal, or coitus interruptus. There is similar direct evidence for other European countries.
In this instance, the decline in fertility was not the result of technical innovations in contraception, but of the decision of married couples to resort to folk methods known for centuries. Thus we must explain the decline in the western European birth rates in terms of why people were willing to modify their sexual behavior in order to have fewer children. Such changes in attitude were doubtless a part of a whole set of profound social and economic changes that accompanied the industrialization and modernization of western Europe. Among the factors underlying this particular change in attitude was a change in the economic consequences of childbearing. In a pre-industrial, agrarian society children start helping with chores at an early age they do not remain in a dependent status during a long period of education. They provide the principal form of support for the parents in their old age, and, with high mortality, many children must be born to ensure that some will survive to take care of their parents. On the other hand, in an urban, industrialized society, children are less of an economic asset and more of an economic burden.
Among the social factors that might account for the change in attitude is the decline in the importance of the family as an economic unit that has accompanied the industrialization and modernization of Europe. In an industrialized economy, the family is no longer the unit of production and individuals come to be judged by what they do rather than who they are. Children leave home to seek jobs and parents no longer count on support by their children in their old age. As this kind of modernization continues, public education, which is essential to the production of a literate labor force, is extended to women, and thus the traditional subordinate role of women is modified. Since the burden of child care falls primarily on women, their rise in status is probably an important element in the development of an attitude favoring the deliberate limitation of family size. Finally, the social and economic changes characteristic of industrialization and modernization of a country are accompanied by and reinforce a rise of secularism, pragmatism, and rationalism in place of custom and tradition. Since modernization of a nation involves extension of deliberate human control over an increasing range of the environment,
it is not surprising that people living in an economy undergoing industrialization should extend the notion of deliberate and rational control to the question of whether or not birth should result from their sexual activities.
As the simplified representation in Figure 1 indicates, the birth rate in western Europe usually began its descent after the death rate had already fallen substantially. (France is a partial exception. The decline in French births began late in the 18th century and the downward courses of the birth and death rates during the 19th century were more or less parallel.) In general, the death rate appears to be affected more immediately and automatically by industrialization. One may surmise that the birth rate responds more slowly because its reduction requires changes in more deeply seated customs. There is in most societies a consensus in favor of improving health and reducing the incidence of premature death. There is no such consensus for changes in attitudes and behavior needed to reduce the birth rate.
DECLINING FERTILITY AND MORTALITY IN OTHER INDUSTRIALIZED AREAS
The pattern of declining mortality and fertility that we have described for western Europe fits not only the western European countries upon which it is based but also, with suitable adjustment in the initial birth and death rates and in the time scale, eastern and southern Europe (with the exception of Albania), the Soviet Union, Japan, the United States, Australia, Canada, Argentina, and New Zealand. In short, every country that has changed from a predominantly rural agrarian society to a predominantly industrial urban society and has extended public education to near-universality, at least at the primary school level, has had a major reduction in birth and death rates of the sort depicted in Figure 1.
The jagged line describing the variable current birth rate represents in some instances&mdashnotably the United States&mdasha major recovery in the birth rate from its low point. It must be remembered, however, that this recovery has not been caused by a reversion to uncontrolled family size. In the United States, for example, one can scarcely imagine that married couples have forgotten how to employ the contraceptive
techniques that reduced the birth rates to a level of mere replacement just before World War II. We know, in fact, that more couples are skilled in the use of contraception today than ever before. (Nevertheless, effective methods of controlling family size are still unknown and unused by many couples even in the United States.) The recent increase in the birth rate has been the result largely of earlier and more nearly universal marriage, the virtual disappearance of childless and one-child families, and a voluntary choice of two, three, or four children by a vast majority of American couples. There has been no general return to the very large family of pre-industrial times, although some segments of our society still produce many unwanted children.
POPULATION TRENDS IN LESS-DEVELOPED COUNTRIES
We turn now to a comparison of the present situation in the less-developed areas with the demographic circumstances in western Europe prior to the industrial revolution. Figure 2 presents the trends of birth and death rates in the less-developed areas in a rough schematic way similar to that employed in Figure 1. There are several important differences between the circumstances in today&rsquos less-developed areas and those in pre-industrial Europe. Note first that the birth rate in the less-developed areas is higher than it was in pre-industrial western Europe. This difference results from the fact that in many less-developed countries almost all women at age 35 have married, and at an average age substantially less than in 18th-century Europe. Second, many of the less-developed areas of the world today are much more densely populated than was western Europe at the beginning of the industrial revolution. Moreover, there are few remaining areas comparable to North and South America into which a growing population could move and which could provide rapidly expanding markets. Finally, and most significantly, the death rate in the less-developed areas is dropping very rapidly&mdasha decline that looks almost vertical compared to the gradual decline in western Europe&mdashand without regard to economic change.
The precipitous decline in the death rate that is occurring in the low-income countries of the world is a consequence of the development and application of low-cost public health techniques. Unlike
World population pyramid since 1800 - Biology
National Populations > Explanation
Some countries, like China, India, and the United States have very large populations while others such as Monaco, Malta and Bhutan have very small populations.
In general, it is the small island nations such as Tokelau, Tuvalu and Nauru that have the world's smallest populations. An interactive table of population sizes by country from 2008-2013 is available from the World Bank.
Not only do different countries have different sized populations but their populations also grow at different rates. A few countries (about 20) including Russia, Hungary, Japan and Greece are not growing any more but have zero or negative growth rates. The World Bank has produced a table of country growth rates from 1980 – 2013.
In the event any of these links become outdated you may visit The World Bank site at 'worldbank.org' and search for them.
National (country specific) populations are affected by a number of factors. Internal growth is affected both by having a higher number of births than deaths and also by having a higher number of immigrants than emigrants. At a national level there are three main drivers of population change, fertility, mortality and migration. Each of these is influenced by complex internal factors, including cultural and religious influences. In addition to these three factors, disease, war and natural disasters can affect national population size and age structure.
For example, the Black Death (plague) in Europe in the mid-1300s was estimated to result in between 75-200 million deaths, World War 1 and World War 2 accounted for about 17 million and over 60 million deaths respectively and the famine following China's Great Leap Forward in 1958-61 resulted in at least 18 million deaths.
We project future populations from current populations (Census data) by adding births, subtracting deaths and adjusting for migration. This involves making assumptions about fertility, mortality and migration rates.
END NATIONAL POPULATIONS EXPLANATION
In order to determine whether a population is growing or in decline we need to understand the structure of a population (how many old and young are in the population) and how this structure is changing over time.
Population pyramids are side-by-side histograms of the population grouped by age and sex, and are used for two purposes:
- To look at the age structure of the population
- To investigate changes in the age structure over time
You can create population pyramids using Microsoft Excel, a sample of which can be downloaded below.
The link below provides time series of population growth and population pyramids for most countries in the world, from populationpyramid.net.
These population pyramids show how the structure of the New Zealand population has changed since the end of the Second World War, and how it is projected to change over the next thirty years.
Looking at population pyramids across time gives a graphical display of the demographic effect of momentum (either that of population growth resulting from a youthful age structure or that of population decline resulting from an older age structure) can be viewed. Jackson (2001) says these 'two trends are often on a seemingly unavoidable collision course'.
Dynamic population pyramids show this process in action, leading up to and beyond the point (different for each country) where natural increase (growth) shifts to become natural decrease (decline). They can also be used to look at 'what if' analyses of population projections.
The easiest way to do this is using a dynamic population pyramid that demonstrates the changes in the age structure across time. Many countries now provide these on the websites of their national statistics office, and some are available on the internet.
Dynamic population pyramids are also a useful tool for comparing the changing age profiles of different countries.
For example, the link below shows the changing age structures in China, Europe and the United States of America.
If the link is outdated go to 'china-profile.com' and look for 'Population by Age and Sex'.
Examples of dynamic population pyramids:
As for the world population, within countries the total fertility rate is defined as the expected number of children a woman would bear through her child-bearing years.
Country specific total fertility rates are influenced by factors such as the country's age structure and life expectancy, individual's desired family size, access to and use of contraceptives, and cultural and religious attitudes to childbirth.
Most countries currently have declining total fertility rates.
The TFR in New Zealand declined in the late 1800s, but rose again after World War 2. It has since declined until reaching a plateau at about 1.96-1.98 (apart from a couple of baby 'blips' in 1991 and 2008).
Source: Statistics New Zealand
As with fertility, age specific mortality rates are also a factor. Each country uses data on mortality (deaths) to work out life expectancy.
The following two graphs give the changing crude death rate (per 1,000) and life expectancy at birth over time in New Zealand.
Source: Statistics New Zealand
Populations have natural increase when there are more births than deaths and natural decline when there are more elderly than children (more deaths than births).
The graph below shows the 'Natural Increase', the births minus the deaths, for New Zealand.
New Zealand: Natural Increase (births minus deaths).
Source: Statistics New Zealand
Migration also influences population growth and some countries are trying to use immigration to change the age structure of their current population.
However, migration trends are often volatile as shown in the graph below for New Zealand and usually measure movements not people. The long-term impact on population growth is not always as expected and may differ across ethnic or national groups.
The graph below tells us the the net permanent/long term migration for New Zealand.
New Zealand Net Permanent/Long Term Migration
Source: Statistics New Zealand
Net Migration (in a given year) = Immigration - Emigration
The next graph shows the net outcome for different population groups in New Zealand.
PLT Migration: Net gain or loss by previous/next country of residence