Is fertility in the U.S. declining? Economist Lyman Stone argues yes. He parsed the numbers in a detailed New York Times report Tuesday. But a recent report from Pew Research Center suggests births are on the rise.

Who’s right? And why does it matter?

Reasons for The Decline

Let’s start with Stone. Why is fertility continuing to drop, despite recovery from the Great Recession?

According to the Center for Disease Control and Prevention, the fertility rate is currently at 1.77 births per woman over her lifetime. This is based on the General Fertility Rate (GFR), which measures fertility rates based on the annual number of births. That rate has dropped 3.8 percent since 2015, and 16.4 percent since 2007. In 2007, the fertility rate was 2.12. Developed countries have a replacement rate of about 2.1.

Stone delves into some reasons why.

One is a decline in teen pregnancy. Last week in Politico, W. Bradford Wilcox of the American Enterprise Institute and Samuel Sturgeon of Demographic Intelligence wrote about American’s declining sexual activity. (Stone also works with Demographic Intelligence.) Like adults, teens are having less sex than in previous generations.

Part of this is because they are more cautious of unintended pregnancy and diseases, Wilcox and Sturgeon note. Another reason could be due to technology. “There is certainly a correlation between the rise of smartphones and the decline of physical sex among young adults,” Wilcox and Sturgeon write.

Most can agree that a decline in teen pregnancy is good. But, as Stone adds, that decline has crept up to include women in their 20s and 30s. 

A second reason is the rising age of first marriage. Young people marry later than ever. The median age for getting married is now 27.4 for women and 29.5 for men. A quarter of millennials are expected to never marry, Time reported in 2014.

As Wilcox and Sturgeon noted in Politico, unmarried people have less sex than married couples. That, combined with use of long-acting reversible contraceptives and emergency contraception, has led to a decrease in unintended births among unmarried women.

A third is the rising average age of first birth. It’s now over 26 in the U.S. That’s lower than other developed nations, but still higher than in years past.

One Problem Solved, Another Remains

The reduced teen and unmarried pregnancy rates are good. Research shows that children do best when their parents are married.

But decreased fertility hasn’t been limited to the underage or the unmarried. As Stone writes, “Americans are improving their ability to avoid unwanted pregnancies far faster than they are improving the ability to achieve desired pregnancy.”

He explains that fertility treatments like IVF and egg storage remain expensive. Stone points to data revealing that women say they want 2.7 children. But looking at the GFR, they’re likely to have just 1.8. The gap between what they want and what they’re likely to get is the widest it’s been in 40 years, he reports. 

Harmful Side Effects

Why does the fertility rate matter? Last week The New York Times highlighted adults who say they are forgoing parenthood due to fear of overpopulation. But overpopulation won’t be the real problem.

“Very real problems could develop from lower fertility that many might not see coming,” Stone argues. He mentions “difficulty meeting Social Security obligations, caring for older people and maintaining economic growth” as possible downsides.

Wilcox and Sturgeon also touch on the dangers of declining birth rates. They list “reduced economic growth, less entrepreneurial activity, and a declining ration of taxpayers to retirees” as problems. They also point to Japan, with a fertility rate of just 1.41:

Japanese companies struggle to find workers, and the government struggles to pay for public pensions. … Japan has the largest public debt of any nation in the world. Most fundamentally, the Japanese way means that millions of people live alone.

Stone sums up his report this way: “millennial women are likely to experience the largest shortfall in achieved fertility versus their stated family desires of any generation in a long time.”

Other Research

While troubling, Stone’s report isn’t the end of the story. Based on other fertility indicators, modern women may still end up with more children than women 10 years ago.

In January, the Pew Research Center revealed that in 2016, 86 percent of women ages 40-44 were mothers. In 2006, only 80 percent of women that age were mothers. Based on this research method, Pew also found that today, women are having 2.7 children on average. Again, that’s up from 2006, when the average was 1.86.

What explains the discrepancy between these numbers and the research Stone, Wilcox and Sturgeon cite? The Pew report uses the completed fertility indicator. The GFR, used by the government, tracks fertility on an annual basis. Completed fertility is the “cumulative measure of lifetime fertility, the number of births a woman has ever had.”

Regardless of which fertility indicator you focus on, a few things are certain. Americans are having less sex. Teen and unmarried pregnancies are down. Couples are waiting longer than ever to marry. Women are waiting longer than ever to have children.

The takeaway? The risks of low fertility rates, often overlooked amid fears about overpopulation, are serious enough to warrant our attention. We should keep a close eye on the trends, and explore ways to not only support existing families, but encourage new ones.