World Population

archive material: updated August 2021

The current world population of 7.8 billion is expected to reach 9.7 billion in 2050. Almost the whole of this growth in population will be located in the world’s developing regions.

In many richer countries, including China, there are increasing signs that population numbers may begin to fall, as women choose to have fewer children. Some experts believe that world population projections may be revised accordingly.

For those countries where population continues to grow strongly, the optimum strategy for stabilising numbers is to achieve universal coverage of reproductive health services and to respect the broader agenda of women’s rights, especially in education. These longstanding objectives are now articulated in the Sustainable Development Goals approved by world leaders for the period 2016-2030.

However, these Goals are not associated with any quantitative targets for global population. Policymaking should strive to create freedom of choice for individuals, respecting their ultimate right to exercise that choice.

Furthermore, a rights-based approach to population goals is no substitute for tackling the excessive and unequal consumption of modern lifestyles. Oxfam research finds that the richest one percent of the world’s population are responsible for more than twice as much carbon pollution as the 3.1 billion people who made up the poorest half of humanity.

Fears for the long term security of the three essential needs of humanity – water, food and energy – signal that our world population can be sustained only if rich and poor alike can be persuaded to embed the principles of sustainability in their consumption and its associated pollution.

There is no denying the pressures of scarcity that future population growth will impose. However, deploying it as a smokescreen for our incompetence in the equitable management of finite resources will not improve our chances.

World Population Projections

On an average day the birth of 360,000 new babies in the world outpaces deaths (in all age groups) by a factor of more than two. As a result the world population increases daily by over 200,000, demanding the equivalent of a new city of almost 1.5 million inhabitants every week. The total passed seven billion in October 2011 and will almost certainly reach eight billion by 2023. The UN’s median projection for 2050 is 9.7 billion.

According to the most recent UN figures, the population of sub-Saharan Africa will double, in contrast to projected falls in Japan and China. India’s population of 1.4 billion is expected to overtake China in 2027; together these two countries may account for almost a third of humanity by 2050.

Accurate population data is a vital tool of social and economic policy, locally, nationally and globally. Governments cannot deliver efficient services or plan long term infrastructure development without knowledge of the national demographic profile – the size of the population, where people live, how old they are, and the net effect of births, deaths and migration.

Compiling this essential information is far from straightforward. The conduct of a census requires professional management, a very large number of enumerators, application of new technologies and skilled interpretation of the results. Nigeria is one example of a country which has had consistent difficulty in delivering reliable census results, doubly unfortunate in that it is Africa’s most populous nation, with a very high fertility rate.

Led by the UN Population Fund, international agencies often provide generous financial and logistical support for census production in developing countries.

The UN strives to ensure that data has value in the global as well as national domain. Its 2020 World Population and Housing Census Programme has engaged the cooperation of almost every country to complete at least one census between 2015 and 2024, adhering to minimum standards.

Every two years, the Population Division of the UN Department of Economic and Social Affairs publishes its World Population Prospects, essentially a “revision” of previous projections. Based on the latest national census results and other surveys, this is the primary source of global population data. Both the overall UN Census Programme and publication of the 2021 Revision may be delayed by the Covid pandemic.

These Revisions concede that the two key variables in world population projections, life expectancy and fertility, are fraught with uncertainty over long projection periods. For example, the significant impact of HIV and AIDS in Southern Africa could not have been anticipated by demographers. The same will be true if Covid-19 proves to have altered trends in fertility and mortality, to a significant extent.

Even a modest error of 0.5 in the assumed total fertility rate (TFR – the average number of children that a woman has in her lifetime) would be sufficient to generate a range of uncertainty of over 2 billion for the 2050 population projection. This sensitivity undermines the accuracy of projections beyond 2050 and is an important influence on strategies to stabilise the world population.

It also explains the wide divergence of opinion in dating “peak population”, the point at which world population begins to fall. The official UN median projection sees the figure rising throughout the 21st century to reach 10.9 billion in 2100. By contrast, many independent researchers believe that the figure will start to fall decades earlier. A 2020 paper published in The Lancet predicts sustained falls in fertility rates so that world population will peak at 9.7 billion in 2064, falling to 8.8 billion by 2100, over two billion fewer than the UN projection.

Demographic Transition

To stereotype the poorest countries with the custom of large family sizes is to turn a blind eye to history. Most people now living in richer countries will discover similar fecundity in their own families by tracing back just a few generations.

The circumstances might have had much in common with contemporary African countries – poverty and high child mortality, dependence on surviving children for economic support, lack of education or job opportunities for women and the unavailability of any form of contraception.

The evolution to lower fertility rates experienced in developed countries correlates with their improving social and economic circumstances. This demographic transition reflects how access to modern medicine combines with greater choice in work, education and lifestyle to lessen the appeal of large families.

In the transition from high to low fertility and mortality rates, the latter has invariably outpaced the former. The consequence is a rapid rise in national population. When the birth rate finally stabilises at its lower level, a country’s population profile will progressively age as the “baby boom” generation matures.

Countries around the world find themselves at very different points within the demographic transition. The headlong rush towards the UN’s projection of a peak global population of almost eleven billion masks a complex mix of underlying trends.

The countries of sub-Saharan Africa are at an early stage of the transition, where child mortality and life expectancy indicators are improving but the average fertility rate of 4.6 children per woman remains high.

The contrast with richer countries is dramatic. The fertility rates in North America and Europe have fallen below 2.1, the threshold for natural population replacement. The same is true of China, so that half of the world’s people live in a country or area where the population is falling.  The strength of this demographic transition is such that the rate of growth of the world’s population has been falling for some time. From a peak of 2.1% per annum in the 1960s, the rate has halved to 1.1%.

Nonetheless, the demographic transition in a hard core of about 20 high fertility countries is slow-moving, with rates remaining stubbornly high. Countries such as Nigeria and Democratic Republic of Congo seem to be trapped in a demographic vortex by poverty and conflict.

Demographic Dividend

A useful indicator for the demographic transition in a country is its “dependency ratio”. This compares the number of juveniles and senior citizens with those of working age who support them, either directly or through government services funded by taxation.

A high dependency ratio is causing considerable concern in mature economies, where funding of health, care and pension provision is inadequate to support ballooning numbers of older people, living ever longer.

By contrast, many poorer countries are at an earlier stage of the demographic transition, with low dependency ratios. In theory these countries should be able to face the future with more confidence, their populations dominated by potentially productive young people. The UN’s World Population Prospects 2019 reports that only 3% of Africa’s population is aged over 65; in Europe the figure is 18%. The economic potential of a low dependency ratio is often described as the “demographic dividend” and has been associated with the tiger economies of East Asia.

In sub-Saharan Africa, it is unclear whether the optimum dependency ratio has been reached. The proportion of children may be too large, not yet economically productive. And the trend to lower fertility rates may be too slow; at current rates Nigeria is considered to be decades away from an advantageous profile. Governments of these countries should be responsive to advocacy for policies which encourage later pregnancies and smaller families.

The demographic dividend is a fleeting opportunity which can quickly overturn into social unrest. Very high rates of youth unemployment do indeed persist in Africa and the Middle East; investment in education and training is desperately needed to ensure that a favourable demographic profile delivers dividends rather than deficits. Indonesia is a country that may be in a position to revive faith in the concept of a demographic dividend..

Aware that the demographic dividend may exist more in theory than substance, many economists interpret the demographic mismatch between richer and poorer countries as a force for migration. This view suggests that the imbalance will be a long term driver of labour migration, ultimately redressing the falling populations of the mature economies.

Overpopulation or Overconsumption?

In the animal world, species move through demographic cycles which typically follow a pattern of “boom and bust.” Rampant reproduction encounters a threshold known as “carrying capacity” beyond which the environmental resources essential to that species deteriorate, leading to a sharp decline in its population. Whether the carrying capacity has been breached through overpopulation or overconsumption is a matter for nature to resolve.

Humans possess the unique power to influence their own carrying capacity on planet Earth. They know the factors that will dictate its level – the global population, the economic capacity of individuals to consume resources, the technologies available and lifestyle choices.

Exercising wisdom in mixing this cocktail is proving highly problematic, largely because our politicians have proved incapable of acting on the warnings of our earth scientists. The extreme inequality that pervades humanity may be to blame for this dysfunction of national and global governance. Very affluent individuals and corporations consume excessive resources and have sufficient power to hold governments to ransom in resisting change.

Such are these extremes that, even if the global population was stabilised tomorrow, the roll-call of environmental threats – climate change, loss of biodiversity, water scarcity – would remain. Studies published by the Stockholm Resilience Centre suggest that four out of nine environmental boundaries critical to a sustainable planet have already been crossed.

Projections of the world population show that its growth will be located almost entirely within low income countries where consumption is a small fraction of that in mature economies. Action to reduce consumption in these richer economies will accelerate prospects for sustainability far more than action to reduce the global population.

The immediate priority is to find a narrower and less damaging range of consumption in which the less fortunate can live in dignity but which in aggregate remains within our planetary boundaries.

The obstacle is our global addiction to a measure of economic success which rewards consumption of resources rather than the sustainability of their use. Economic “growth”, as currently quantified, is arguably far more damaging to the planet than population growth, yet is relentlessly pursued.

The Sustainable Development Goals approved in 2015 include Goal 12: “ensure sustainable consumption and production patterns.” However, the targets make no reference to the necessary reforms in measuring economic “growth”.