Although you wouldn't know it from the constant barrage of pregnant celebrity pics on social media, the fertility rate in the US—the number of births per 1,000 women ages 15 to 44—fell to 60 last year, its lowest level since the government started tracking the figure in 1909, reports NPR. Per the Centers for Disease Control and Prevention, the birth rate is down in nearly every age group tracked. The 3,853,472 births in the US last year represent a 3% drop from 2016, the largest single-year decline since 2010 and the fewest babies born in one year since 1978. A country’s fertility rate is an important measure of its sustainability, reports the New York Times. Too many births put a strain on education and housing. Too few births, and over time the labor pool declines, which in turn tightens resources. In the US, the decline has not yet led to a drop in overall population, because it has been offset to some degree by immigrants.
The decline is a bit surprising because in 2017 there were about 7% more women in their prime childbearing years of 20 to 39. One group that ran against the trend was older women. The birth rate among women age 40 to 44 was up 2% over the previous year. In fact, almost one in five births were to women 35 or older. Although it’s difficult to say for certain what's causing the decline, several factors may be at work, including economic uncertainty stemming from the economic downturn in 2007, reports LiveScience. In addition, women have been waiting longer to have children, and millennial women appear to be waiting even longer than previous generations as they build their careers. One happy finding: Births in the 15 to 19 age group were down 7%, down 55% since 2007, and down 70% from a high in 1991, a trend one statistician called "phenomenal." (Read more birth stories.)