World population predicted to shrink after the mid-century

According to a new study, world population will peak in 2064 at around 9.7 billion and then decline to 8.8 billion by 2100 – around 2 billion lower than previous estimates

The new study, published in the Lancet, found that improvements in access to modern contraception, sustained declines in fertility, and the education of girls and women will cause the world population to shrink after the mid-century.

The research used data from the Global Burden of Disease Study 2017 to project future global, regional, and national population.

Researchers from the University of Washington’s School of Medicine estimate that by 2100, 183 countries will have total fertility rates (TFR), meaning the average number of children a woman delivers over her lifetime is below 2.1 births per woman. Therefore, populations in these countries will decline unless low fertility is compensated by immigration.

The new forecasts go against the UN projections of ‘continuing global growth’, and highlight the huge challenges that will face economies, health and social support systems and global powers.

A shifting global age structure

The new study also predicts there will be around 2.37 billion individuals over 65 years globally in 2100, compared with 1.7 billion under 20 years.

Stein Emil Vollset, first author of the paper, said: “Our findings suggest that the decline in the numbers of working-age adults alone will reduce GDP growth rates that could result in major shifts in global economic power by the century’s end. Responding to population decline is likely to become an overriding policy concern in many nations, but must not compromise efforts to enhance women’s reproductive health or progress on women’s rights.”

A decline in global fertility

The global TFR is predicted to steadily decline, from 2.37 in 2017 to 1.66 in 2100, with rates falling to around 1.2 in Italy and Spain, and as low as 1.17 in Poland.

TFR rates are likely to reduce the most in high-fertility countries, particularly such as those in sub-Saharan Africa. Rates are expected to fall below the replacement level for the first time, from 4.6 in 2017 to 1.7 by 2100.

In Niger, where the fertility rate was the highest in the world at 7 in 2017, the rate is projected to decline to around 1.8 by 2100.

However, the population of sub-Saharan Africa is still likely to triple over the course of the century, as death rates decline and as more women enter reproductive age.

Many of the fastest-shrinking populations will be in Asia and central and eastern Europe. Populations are expected to more than halve in 23, including Japan, Thailand, Spain and Italy. An additional 34 countries are expected to have population declines of 25 to 50%, such as China.

Decreasing working-age populations

The study also examined the economic impact of fewer working-age adults globally.

While China is set to replace the USA in 2035 with the largest total gross domestic product (GDP) globally, rapid population decline from 2050 onward will curtail economic growth. Therefore, the USA is expected to reclaim the top spot by 2098, if immigration continues to sustain the US workforce.

Numbers of working-age adults in India are predicted to decline from 762 million in 2017 to 578 million in 2100. Although it is expected to be one of the few major power in Asia to protect its working-age population over the century.

Sub-Saharan Africa is likely to become increasingly powerful on the geopolitical stage as its population increases. Nigeria is projected to be the only country among the world’s 10 most populated nations to see its working-age population grow over the course of the century (from 86 million in 2017 to 458 million in 2100).

The UK, Germany, and France are expected to remain in the top 10 for largest GDP worldwide. However, Italy (from rank 9th in 2017 to 25th in 2100) and Spain (from 13th to 28th) are projected to fall, reflecting population declines.

Although the study uses the best available data, predictions are constrained by the quantity and quality of past data. Furthermore, past trends are not always predictive of what will happen in the future, and some factors not included in the model could change the pace of fertility, mortality, or migration.

For example, the COVID-19 pandemic has affected health systems throughout the world, and caused over half a million deaths. However, the authors believe the excess deaths caused by the pandemic are unlikely to significantly alter longer term forecasting trends of world population decline.

Ibrahim Abubakar, chair of Lancet Migration, said: “Migration can be a potential solution to the predicted shortage of working-age populations. While demographers continue to debate the long-term implications of migration as a remedy for declining TFR, for it to be successful, we need a fundamental rethink of global politics.

“The Anthropocene has created many challenges such as climate change and greater global migration. The distribution of working-age populations will be crucial to whether humanity prospers or withers.”