The total fertility rate — or the average number of children a woman would have if she lived through all her reproductive years — declined from 4.7 live births in 1950 to 2.4 in 2017.
Meanwhile, the global population has nearly tripled since 1950, from 2.6 billion people to 7.6 billion, the report says. An average of nearly 84 million people have been added to the Earth’s population every year since 1985.
Other factors have been shown to predict falling fertility rates, including better infant survival rates and later marriage.
“Marriage is one of the biggest drivers of having children all over the world,” said Kiarie, who is not an author on the new report.
‘The world is really divided’
While total fertility rates fell across all 195 countries and territories in the data, they were split roughly down the middle between those below replacement level and those above, Murray said. “Replacement” describes the total fertility rate “at which a population replaces itself from generation to generation, assuming no migration,” which comes out to about 2.05 live births, the authors say.
For example, a woman in Cyprus had one child on average in 2017, while a woman in Niger had 7.1. This range is lower than 1950’s, in which total fertility rates ranged from 1.7 live births in Andorra to 8.9 in Jordan.
“The world is really divided into two groups,” Murray said. “In a generation, the issue’s not going to be about population growth. It’s going to be about population decline or relaxing immigration policies.”
In countries that want to boost fertility rates, the creation of financial incentives for families, including parental leave, has been shown to have a small effect, Murray said. Only 33 countries, largely in Europe, were falling in population between 2010 and 2017, according to the report.
“The country that’s probably the most concerned about this already is China, where the number of workers is now starting to decline, and that has an immediate effect on economic growth potential,” Murray said. “In a place like India — that is still above replacement but very soon going to be below replacement fertility — that’s just such a dramatic change.”
In just the past several years, Kiarie said, parts of Africa and Asia have substantially lowered fertility rates. The countries that have seen the sharpest declines are those that previously had lower rates of contraception, where the introduction of family planning made a more significant impact, he added.
“There’s been rapid progress, but I think in terms of … the areas which have the biggest unmet need for family planning, it’s still largely in Africa,” he said.
Lifestyle continues to kill millions
Lifespans have also gotten longer on average since 1950, climbing from 48.1 to 70.5 years for men and from 52.9 to 75.6 years for women, according to the study. However, the study authors say that just because women live longer doesn’t mean they are living in better health.
When it comes to fertility rates, Kiarie said that the UN goals “are about the ability for people to have the number of children they want,” as well as when and with whomever they choose. “What is key is for that ability to be there, in the women’s hands.”
What often gets lost in discussing fertility statistics and population numbers, Kiarie said, is the focus on individual people, their desires and how countries can empower them to achieve those goals.
“How can we ensure that people do what they think is right for themselves?” he asked.
CNN’s Yemisi Adegoke contributed to this report.