The declining American birth rate is unlikely to bounce back, new study says

• The US fertility rate likely won't rebound, according to a new Brookings report.
• Brookings forecasted fertility rates based on age cohorts and found lower lifetime fertility.
• The trend follows a decade of declining births and falls in line with worldwide birth patterns.

Today's baby bust looks unlikely to turn into a delayed baby boom.

That's according to the latest research from Melissa S. Kearney and Phillip Levine at the Brookings Institution, who say that births in the US are unlikely to rebound. The research comes on the heels of a recent CDC report that found the US birth rate fell by 4%, the sharpest single-year decline in nearly 50 years and the lowest number of births since 1979.

The total fertility rate - or the number of live births a woman is expected to have over her lifetime - also fell from 2.12 in 2007 to 1.64 in 2020, below the 2.1 replacement fertility rate needed for the population to naturally replace itself.

Declining birth rates during an economic downturn are typical. But the recession of 2020 was paired with a global health crisis, which could yield a stronger impact. Demographers are currently debating whether the current drop will prove to be a temporary or permanent phenomenon: Will women will end up having babies at a later date or have fewer babies overall?

Brookings' analysis implies the latter, that US fertility rates will be below replacement levels for the forseeable future. Considering that women who were born in 1975 to 1980 had an average of around 2.2 total lifetime births, Brookings took a look at expected lifetime births for more recent age cohorts.

It forecasted the total number of children ever born based on simulated age profiles of women in the 1985 to 2000 birth cohort under conservative, moderate, and aggressive scenarios. For each cohort, the total number of children ever born per woman continues to further fall. The forecasted fertility rate for the 2000 cohort is 1.44 conservatively, 1.77 moderately, and 1.92 aggressively, all well below the replacement fertility rate.

That is all to say, women are expected to have fewer babies going forward.

A decline in births could reshape the economy

This trend isn't just another fallout from the pandemic, according to Brookings. It follows a decade of declining births for multiple cohorts of women as they wait to have babies until a later age. The simulated fertility rates, Kearney and Levine wrote, are similar to those in high-income countries.

Christine Percheski, associate professor of sociology at Northwestern University, recently told Insider that the US has been slow to fall in line with worldwide birth trends. "It's about women having access to education and employment opportunities," she said. "It's about the rise in individualism. It's about the rise in women's autonomy and a change in values."

Macroeconomic forces are another major factor in the decision to postpone having kids, a reflection of how expensive the US economy has become. Millennials have grappled with the lingering effects of the Great Recession and soaring living costs for things like housing and, of course, childcare.

If Brookings' analysis proves to be true, experts are worried the US is entering a demographic crisis that would result in an economy with an aging population that isn't replaced by enough young workers. It could yield higher government costs and a smaller workforce that would have to front the care costs for aging populations, creating a shortage of pension and social security-type funds.

Read more: The declining American birth rate could actually be good for the economy

But Mauro Guillén, Wharton professor and author of "2030: How Today's Biggest Trends Will Collide and Reshape the Future" told Insider in April that the decline in births is a "temporary blip," likely to last one to two years.

"Young couples have said, 'Give me a rain check, I don't want the baby now because there's too much uncertainty,'" he said. "But they will have those babies later. They don't cancel their plans to have babies for life."

Regardless of what happens, a declining birth rate doesn't have to mean devastation for the economy. It will undoubtedly be an economic shift, but such change isn't necessarily bad. It just requires structural adjustments, like creating new policies that accommodate to changes in population in size, and for people to welcome a reshaped economy with open arms.