A study published in The Lancet medical journal in November 2018 reported that global fertility rates decreased dramatically between 1950 and 2017. If that sounds worrying — especially if you’re used to hearing tired comments about your ticking biological clock — fear not: It’s less about biology, and more about statistics. Using data from 195 countries, the researchers found that in 1950, the average woman or person assigned female at birth (AFAB) delivered 4.7 live births. But by 2017, that number had dropped by nearly half (49.4 percent, to be exact) to 2.4. In 102 of those countries, the rate had decreased by more than half. But why, and what does it mean? Here are a few fascinating nuggets this study found out and how they could change the world.

Baby and mom smiling at camera

1. What is the fertility rate?Dr. Beth McAvey, a reproductive endocrinologist and fertility specialist for the Glow Fertility Program, explains that for the purposes of this study, “The total fertility rate measures the average number of children a woman/person AFAB could have if they survived through the end of their reproductive span [defined in the study as age 10 to 54].” To work this out, the researchers estimated the annual number of live births in a specific age group per thousand people AFAB. For example, in Cuba, on average, 84.1 people AFAB aged 25 to 29 delivered a live birth. The researchers compiled all of this information to work out the total fertility rate (TFR) on average for each country and for the world.

2. The fertility rate can be drastically different depending on where you live. Overall, people are having fewer children, but that fact alone masks a wide variation in family size around the world. The study reports the fertility rates in each of the 195 countries and in different regions, giving a picture of the trends on a national level. Dr. Joshua U. Klein, a reproductive endocrinologist and chief medical officer at Extend Fertility and Expect Fertility, says, “This study shows that while overall fertility rates are declining on average, there is a wide region-specific variation in this trend that correlates with factors like education and access to reproductive health services — for example, contraception and abortion.” As an example of the disparities, in 2017 Cyprus had the lowest TFR, with people giving birth to an average of one child, while in Niger, home to that year’s highest TFR, the average number of live births per woman/person AFAB was 7.1.

3. The global population is still rising. Even though people are having fewer babies on average, the study found that the global population has been increasing by an average of 83.8 million people a year since 1985 and is now the highest it’s ever been. Between 1950 and 2017, the global population rose from 2.6 billion to 7.6 billion. According to Dr. Daniel Kort, an OB/GYN and reproductive endocrinologist with Neway Fertility, “This study confirms much of what the scientific community has suspected about population growth in the past century: While the number of births per person is overall decreasing, the overall population is increasing as people are living longer.” That said, as with the TFR, population growth varies around the world. Between 2010 to 2017, 33 countries, mostly in Europe and in the Caribbean, saw a negative population growth rate, meaning more people died and/or emigrated than were born. Meanwhile in sub-Saharan Africa in 2017, the population grew at 2.7 percent, nearly the all-time high for the region and significantly higher than the global average of 1.1 percent.

4. On average, people are having babies later. People are waiting longer to have babies, and there are fewer teen births. The global average number of live births reported for 10- to 19-year-olds decreased from 37 per 1000 women/people AFAB in 1950 to 22 per 1000 women/people AFAB in 2017. On the other side, since 1975 the total fertility rate for women over 30 in western, central and eastern Europe; North America; Australasia; and high-income areas of Asia Pacific has increased by 60.2 percent. In 145 countries in 2017, fertility rates were higher for women over 30 than for women 25 and under. IVF and fertility nurse Suzie Welsh, who is the founder and CEO of personalized supplement service BINTO, commented, “Women in more advanced economies are waiting longer for their first pregnancy and are bearing fewer children. More women use methods of birth control, stay in school, and stay in their careers longer.”

5. These results could be a positive sign of empowerment for people assigned female at birth. “There are many reasons for the decline in the average number of births, most of which I suspect involve social change throughout the world,” says Kort. “Women now have more control of their own reproduction owing to education, contraception, and changing social norms around the world.” The authors of the study specifically point to three major factors that frequently correlate with lower total fertility rates: Lower mortality rates for children under five, and more people AFAB having access to education, and to effective contraception and reproductive health services. Dr. John S. Rinehart, founding partner of Reproductive Medicine Institute, explains, “The educational level of women and people AFAB is a very strong correlate to the number of children they will have: The higher the education level, the fewer children.” This could be, he says, because “the use of contraception is higher in higher educated women.”

The study also notes a number of other social, political, and economic factors that affect the number of children being born. The researchers specifically point to a population decline in Syria as symptomatic of the way conflict can impact fertility rates and migration: But they also added that sometimes a large war can prompt more people to marry younger, which often leads to them having more children sooner. Rinehart adds, “Rising housing prices and increased women/people AFAB in the workforce may also affect the TFR,” as can political decisions like China’s one-child policy, which saw the country’s TFR drop, only for it to rise once the policy was lifted.

6. What does this mean for the world? It depends where you live, but fewer people being born combined with a population that’s living longer means that there will likely be a shift toward an older world’s population. The study found that the global average age in 2017 was 32.1, compared to 26.6 in 1950. The researchers point to previous studies that found that countries see an economic boost when 65 percent of the population is of working age: While many high-income countries reached that in the 1960s, the ratio started to slide starting in 2005. By 2017, in 12 of 34 high-income countries, less than 65 percent of the population was of working age, and in Japan, it was less than 60 percent.

This trend could potentially impact the economies of those countries, warns Dr. Norbert Gleicher, medical director and chief scientist at the Center for Human Reproduction in New York City. “Fewer people in a country usually means declines in economic output, less consumption, less wealth, et cetera. It also usually means worker shortages and a need to ‘import’ workers, which can have great societal impact. For example, Japan, which was very restrictive for foreign workers, just announced half a million open jobs for foreigners for the first time.” Adjusting for population changes could lead to further opportunities for greater equality: The researchers suggested that that 65 percent target is a good incentive for developing countries, in particular, to focus on educating young girls and children assigned female at birth so they can join the workforce.

Overall, this well-researched study provides useful information for governments looking to adapt to shifting population dynamics. “As population and fertility data become more and more accessible, models to predict the future will become more and more reliable,” Kort says. “Policymakers will ultimately be able to use these models to allocate resources and make effective decisions for the future.” See you for the update in 67 years!

Do you have fewer kids than the generations before you? Share your take on this fascinating study @BritandCo.

(Photo via Getty)