Causes of drop in birthrates under debate

Global population could start to fall by 2040 if trends continue, experts say

In developed nations, couples just aren't making babies like they used to.

The fertility rate-the average number of children a woman gives birth to in her lifetime-has been dropping since 1950.

According to The Lancet, a British medical journal, in 1950 women worldwide gave birth to an average of 4.7 children. By 2017, the number had fallen to 2.4 children per woman.

But the fertility rate has fallen below the replacement level of 2.1 live births per woman in many nations and regions, including the United States (1.80), Japan (1.62), the European Union (1.59) and China (1.44), the World Bank reported.

At current levels, total populations will decline over time. An average of slightly more than two babies per woman is needed to replace the current population because not all children survive to adulthood, not all women marry, not all who marry have children, and there are slightly more males born than females, demographers say.

"Fewer young adults see marriage as important for personal life satisfaction or a necessary prerequisite for having children," Jonathan Abbamonte, a research analyst at the non-profit Population Research Institute in Virginia, told China Daily in an email.

"Young adults today are postponing marriage later and later in adulthood, reducing the number of years a couple has for having children."

But fertility rates remain high in many underdeveloped nations. In sub-Saharan Africa, the fertility rate in Niger is 7.1 children, 6.7 in Chad and 6.1 in Somalia. Worldwide, 91 nations aren't producing enough children to maintain their current populations, but 104 other nations have high birthrates leading to population increases, the Institute for Health Metrics and Evaluation in Seattle reported.

If present trends continue, demographers believe the world's population will start to decline by 2040. Over time, that could lead to a world with more grandparents than grandchildren, making the current world unsustainable as the labor force shrinks, markets decline and there are fewer tax-paying workers to support retirees, research papers have concluded.

Researchers don't fully understand the reasons for declining fertility rates but point to several possible causes: greater access to contraception, wide availability of abortion and increased educational opportunities, especially for women.

"Young adults are staying in school longer and as a result, the timetable is longer for them to become established in their career and to feel secure enough to start a family," Abbamonte said.

Others point to environmental factors. Research by the World Health Organization suggests that pollution could disrupt the endocrine system, the glands that produce hormones regulating growth, metabolism and sexual function.

Research articles published in Human Reproduction Update, a British journal focused on obstetrics, gynecology and reproductive biology, report that in the past 50 years, sperm counts have dropped, testicular cancer has increased, and testosterone levels have declined.

Role of intervention

So far, government intervention hasn't significantly boosted the number of births. The reason may be simple: Parents want the best for their children and therefore have smaller families.

The US Bureau of the Census said many well-educated women build a career first and have fewer children later in life, underscoring a long-term trend: family size typically declines as educational level rises.

Russia's fertility rate is 1.48-well below the 2.1 replacement level but above 1999's rate of 1.16, the World Bank reported.

Russian President Vladimir Putin has proposed extending to first-time mothers maternity benefits previously offered only to women with two or more children. Welfare benefits would be available to children aged 3 to 7 in low-income families, and free meals would be available in the first four years of school, news reports say.