World Populations May Shrink After Mid-Century

The world's population may top out at roughly 9.7 billion around 2064, up from about 7.8 billion today, before shrinking to 8.8 billion by the end of the century, according to estimates published in the journal The Lancet.

The estimate contradicts the forecast from the United Nations Population Division, which expects the population in 2100 to be 10.9 billion and rising.

If it proves to be correct, however, the consequences of a shrinking population would be far-reaching.

It would be great news for the environment, but bad news for the economy, as there would be fewer workers and consumers, and a smaller workforce would have to support a larger elderly population.

Fertility rates have been declining worldwide largely due to improvements in education and access to birth control for women. The main difference between the new forecast and the UN's is what they expect to happen after fertility rates bottom out.

Populations hold steady when women have an average of just over two children each, which is called the replacement rate. Across wealthier countries, the average fertility rate currently is closer to 1.6. In Japan, Singapore and Italy, it is just 1.3.

The UN assumes fertility rates will rise again over time to 1.75, but study co-author Chris Murray disagrees. By 2100, his group estimates that nearly every country in the world will be below the replacement rate. Populations in 23 countries, including Japan, Thailand and Spain, would be half of what they were in 2017. Another 34 would lose between a quarter and a half of their citizens. China is expected to lose 48%.

Murray said countries have three options to keep themselves afloat.

"One is to make it easier for women to work and have children," he said, including generous parental leave and support for working mothers with young children.

The second option is to open their borders to immigration.

And Murray worries that countries might be tempted by the third option: rolling back women's reproductive health rights to pressure them to have more children.