The toll of the COVID-19 pandemic was reflected in a natural decrease last year in the population of nearly three-quarters of U.S. counties versus the two previous years, the census bureau said on Thursday.

More than 73% of U.S. counties experienced natural decrease, or an excess of deaths over births, up from 55.5% in 2020 and 45.5% in 2019, bureau data showed.

"In 2021, fewer births, an aging population and increased mortality – intensified by the COVID-19 pandemic - contributed to a rise in natural decrease," the U.S. Census Bureau said in a statement.

The biggest loss, of 159,621 residents, was in Los Angeles county in California, according to the data released by the bureau, as part of its Vintage 2021 estimates of population and components of change.

All counties in Delaware, Maine, New Hampshire and Rhode Island experienced natural decrease in 2021, it added, while migration also led to a decline in population for some.

The fall continues a trend in which more than half of all U.S. counties lost population over the decade from 2010, with almost all growth taking place in metropolitan areas, census officials said last August.

Between 2020 and 2021, population increased in about 65% of metropolitan areas within the 50 U.S. states and the District of Columbia.

The U.S. population grew at a slower pace in 2021 than any other year on record as the COVID-19 pandemic worsened the more subdued growth of recent years, the bureau has said.