America’s weak population growth, already held back by a decadelong fertility slump, is dropping closer to zero because of the Covid-19 pandemic.

In half of all states last year, more people died than were born, up from five states in 2019. Early estimates show the total U.S. population grew 0.35% for the year ended July 1, 2020, the lowest ever documented, and growth is expected to remain near flat this year.

Some demographers cite an outside chance the population could shrink for the first time on record. Population growth is an important influence on the size of the labor market and a country’s fiscal and economic strength.

One bad year doesn’t automatically spell trouble for future U.S. demographic health. What concerns demographers is that in the past, when a weak economy drove down births, it was often a temporary phenomenon that reversed once the economy bounced back.

Yet after births peaked in 2007, they never rebounded from the nearly two-year recession that followed, even though Americans enjoyed a subsequent decade of economic growth.