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Americans have been having , with fertility rates dropping by more than half—and as a result, the country's population is quickly growing older.

In terms of reproductive rights, declining fertility rates are a sign of successful advocacy. From an economic perspective, however, a healthy birth rate is crucial to ensuring enough workers exist to keep the engines of the economy strong and provide care for older generations. Japan is struggling with this exact problem right now. In 2015, the United Nations estimated that , but Japan only had around two. By 2050, Japan's population is slated to drop by 15%, as elders pass on and newborns become less common.

partnered with Â鶹ԭ´´ to further explore the falling fertility rates in the U.S. with , and what it means for future demographics. While fertility rates are calculated based on a country's female population of childbearing age, Northwell Health and Â鶹ԭ´´ recognize that some people in that group may not identify as women.

Some countries, like Singapore, have tried to boost declining birth rates with "" like cash gifts to parents with multiple children, extending parental leave, and giving couples with children priority in public housing assignments. But despite , which also included grants to companies that give workers more schedule flexibility to accommodate family needs, Singapore's fertility rate continued to fall, from 1.41 to 1.16.

Poh Lin Tan, a public policy scholar at the National University of Singapore, concluded in a report for the International Monetary Fund that Singapore's attempts to redirect fertility trends aren't due to poor policies, but rather are a testimony to "the overwhelming success of an economic and social system that heavily rewards achievement and penalizes lack of ambition."

It's a similar story in South Korea, where the pressure to ensure children have all they need to succeed—like expensive tutoring—discourages people from having large families, according to Richard Jackson, president of the Aging Institute, who was .

In the U.S., time will tell if the Biden administration's will boost fertility—but an , a senior fellow at the Public Policy Institute of California, indicates some may have helped. However, he says the net effect is generally not enough to bring the population back from the brink of decline.

Pinpointing the factors that have led to sustained fertility rate declines in the U.S. is puzzlingly complex. In the , scholars at the University of Maryland and Wellesley College find no relationship between the drop in childbearing and various other factors, such as religion or the financial stresses of student debt and rent prices.

Until the 1990s, women with higher educational levels had fewer children than those with less education. However, found that in the U.S., higher-educated women have higher fertility rates than women with an undergraduate degree or below. That's possibly due to greater financial stability and more opportunities to support raising children while having a career.

that lower fertility rates are related to higher rates of obesity and increasing urbanization, which leads to higher housing costs. Contraceptive use has undoubtedly affected rates, especially through the —and teen pregnancy has dropped . However, recent state-level abortion bans have made it more tricky to track the effects of policies on fertility.

Immigration, which is responsible for , is one solution to increasing the U.S. population. But fewer young immigrant women are arriving in the U.S., according to a with Kenneth Johnson, senior demographer at the University of New Hampshire. In fact, than arrived.

President Joe Biden's pledge to legalize undocumented, foreign-born residents announced in the first few months of his administration could help immigrants feel more comfortable settling in the U.S., but his proposal doesn't have enough congressional support to pass. Immigrants' boost to U.S. fertility rates may be short-lived, according to one scholar's analysis: sharply as its members find strong educational and work opportunities.