UN Population Projections Paint a Changed Global Demographic over the Next Decades

16 Jun 2019

The UN’s 2019 ‘World Population Prospects’ presents population estimates underpinned by analyses of historical demographic trends. The estimates and projections presented here describe two of four demographic megatrends (population growth and ageing).

The world’s population continues to grow, albeit at a slower pace than at any time since 1950. The growth rate of the world’s population has slowed since its peak of 2.1% a year, falling below 1.1% per year in 2015-2020, a decrease projected to last through the end of this century. The predicted global population of  8.5 billion in 2030, 9.7 billion in 2050 and 10.9 billion in 2100 assumes a decline of fertility for countries where large families are prevalent, a slight increase of fertility in several countries where women have fewer than two live births on average over a lifetime, and continued reductions in mortality. There is inherent uncertainty in population projections due to the global range of plausible future trends in fertility, mortality and international migration, yet this analysis confirms the aforementioned forecasts as  95% certain.

Thus, the size of the world’s population will almost certainly rise over the next few decades. Later in the century, although a continued increase of the global population is considered the most likely outcome, there is roughly a 27% chance that the world’s population could stabilize or even begin to decrease sometime before 2100. Sub-Saharan Africa will account for most of the growth of the world’s population over the coming decades, while several other regions will begin to experience decreasing population numbers.

Of the additional 2.0 billion people who may be added to the global population before 2050, roughly half will be in sub-Saharan Africa, and a quarter in Central and Southern Asia. Sub-Saharan Africa is projected to become the most populous of the eight geographic regions (hereafter “regions” or “SDG regions”) around 2062. Currently, the two most populous regions are Eastern and South-Eastern Asia and Central and Southern Asia. The combined population of Europe and Northern America is stabilizing, projected to grow slowly until around 2042 and decline thereafter to about 1.12 billion at the end of the century. The population of Latin America and the Caribbean, which more than tripled in size between 1950 and 2019, is projected to peak at just below 768 million around 2058 and decline thereafter to about 680 million in 2100. The population of Oceania – excluding Australia and New Zealand, is projected to continue to grow through the end of the century, increasing to 19 million in 2050 and 26 million in 2100. Australia and New Zealand, which are home to 30 million people in 2019, could see their population grow to 38 million in 2050 and 49 million in 2100, according to the medium-variant projection.

Globally, the generation of young people now entering their reproductive years is larger than their parents’ generation. Thus, even if the global level of fertility were to fall immediately to around two births per woman, the number of births would still exceed the number of deaths for several decades, and the world’s population would continue to grow. The implication of the current population age structure for future population growth is called “population momentum” and can be assessed at the global level by projecting the population while assuming that (a) mortality rates remain constant at current levels; and (b) fertility instantly equals the replacement level associated with the current level of mortality.

A comparison of the projected size of the world’s population according to the medium variant and the ‘momentum scenario’ indicates that 68% of global population growth between 2020 and 2050 is implied by the current population age structure.

The remaining 32% of the growth projected by the medium variant is due to fertility above the level required to balance mortality, as well as improvements in survival, that are considered likely over that period. After 2050, the population size projected by the momentum scenario gradually levels off at around 9.3 billion, and the impact of the current age structure on projected growth between 2050 and 2100 is negligible.

This assessment of population momentum implies that over the short term, between 2020 and 2050, only a limited portion of world population growth can be influenced by policies that slow or accelerate fertility decline. In regions where fertility has declined recently such that it is close to two births per woman over a lifetime, including Central and Southern Asia and Latin America and the Caribbean, virtually all of the projected population growth between now and 2050 will be driven by relatively youthful population age structures.

By contrast, in regions where lifetime fertility remains well above two births per woman, such as sub-Saharan Africa and Oceania, population momentum accounts for 42 and 58%. Between 2019 and 2050, the populations of 18 LDCs, all in sub-Saharan Africa, have a high probability of at least doubling in size, while in one country, Niger, the population is projected to nearly triple by 2050. Most of the LDCs that are expected to double in population size are the world’s poorest countries. Several of the least developed countries that are experiencing rapid population growth are Small Island Developing States (SIDS) for which the challenges to achieving sustainable development are compounded by their vulnerability to climate change, climate variability and sea-level rise.

More than half of the projected increase in the global population to 2050 will be concentrated in just nine countries: India, Nigeria, Pakistan, Democratic Republic of the Congo, Ethiopia, the United Republic of Tanzania, Indonesia, Egypt and the United States of America. Current projections indicate that India will surpass China as the world’s most populous country around 2027. After this re-ordering between 2019 and 2050, the ranking of the five largest countries is projected to be preserved through the end of the century, when India could remain the world’s most populous country, followed by China, Nigeria, the United States, and Pakistan. In these regions, future growth is additionally driven by levels of fertility above the level required to balance mortality and yield zero growth over the long run.

Continued rapid population growth presents challenges for sustainable development, as the total population of the least developed countries as a group is growing 2.5 times faster than the total population of the rest of the world.

A growing number of countries are experiencing a decrease in population size due to sustained low levels of fertility and, in some places, high rates of emigration. In 14 of the 27 countries or areas where the population declined by at least one percent between 2010 and 2019, the rate of natural increase was negative over that period, that is, the number of deaths exceeded the number of births. In 23 of the 27 countries or areas where the population declined between 2010 and 2019, more people left the country than arrived, that is, net international migration was negative. Between 2019 and 2050, 55 countries or areas are expected to see their populations decrease by at least one percent.

In some parts of the world, populations are still relatively young. In some countries, the number of people of working age is growing faster than other age groups, creating a window of opportunity for rapid economic growth known as the ‘demographic dividend’. Although the populations of all countries are expected to grow older within the foreseeable future, populations will remain relatively young, at least for the short term, in regions where fertility is still high. Of the eight SDG regions, the proportion of the population of working age is highest in Eastern and South-Eastern Asia, where 56% are aged 25 to 64 years in 2019. This age group accounts for more than half of the population in Europe, Northern America and Australia/New Zealand as well. However, as a result of population ageing the projections indicate that by 2050 the proportion aged 25 to 64 years will fall below 50% in each of these regions.

Historically low levels of fertility combined with increased longevity ensure that populations in virtually all countries and areas are growing older. In 2018, for the first time in human history, pepole over 65 outnumbered children under five worldwide. Between 2019 and 2050, the number of people aged 65 or over globally is projected to more than double, while the number of children under five is projected to remain relatively unchanged, so there will be more than twice as many older people as children under five in 2050.

Whereas the overall numbers of males and females globally are about equal, women outnumber men at older ages owing to their longer average life expectancy. In 2019, women comprise 55% of those aged 65 years or over and 61% of those aged 80 years or over globally. Europe and Northern America have the most aged population in 2019, with 18% aged 65 or over, followed by Australia/New Zealand (16%). Both regions are continuing to age further. Projections indicate that by 2050 one in every four people in Europe and Northern America could be aged 65 years or over.

Sub-Saharan Africa, which has the youngest age distribution of the eight SDG regions, is also projected to experience population ageing over the coming decades, but to a much lesser extent, with the percentage of the population aged 65 or over rising from three percent in 2019 to around five percent in 2050. The number of people above age 80 years is growing even faster than the number above age 65. In 1990 there were just 54 million people aged 80 or over in the world, a number that nearly tripled to 143 million in 2019.

Population ageing will have a profound effect on the potential support ratio, defined here as the number of people of working age (25 to 64 years) per person aged 65 years or over. In 2019, sub-Saharan Africa has 11.7 persons aged 25 to 64 for each person aged 65 or over. This ratio is 10.2 for Oceania, 8.3 for Northern Africa and Western Asia, 8.0 for Central and Southern Asia, 5.8 for Latin America and the Caribbean, 5.0 for Eastern and South-Eastern Asia, 3.3 for Australia and New Zealand, and 3.0 for Europe and Northern America. At 1.8, Japan in 2019 has the lowest potential support ratio of all countries or areas with at least 90,000 inhabitants. An additional 29 other countries or areas, mostly in Europe and the Caribbean, have potential support ratios below three.

By 2050, 48 countries, mostly in Europe, Northern America, Eastern Asia or South-Eastern Asia, are expected to have potential support ratios below two. These low values underscore the potential impact of population ageing on the labor market and economic performance as well as the fiscal pressures that many countries are likely to face in the coming decades in relation to public systems of health care, pensions and social protection schemes for older people.

 

Extract of UN DESA Population Division, ‘World Population Prospects 2019 - Highlights’ (June 2019). Available here.