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.
more Population briefings (updated August 2021)
Opposition to Family Planning
Overpopulation or Overconsumption?
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