This map shows how much every US county's population grew or shrank last year

Some places saw their populations drop, including New York County, which had the biggest percent decline among large counties.

• The Census Bureau published new population estimates for every county in the US.
• New York County, New York, saw the largest percent decline from July 1, 2020 to July 1, 2021 among large counties.
• The above map shows just where populations grew, and which counties saw their numbers shrink. 

Counties grew and shrunk across the US last year, based on new population estimates.

The number of residents changed in various counties as some people moved away to other parts of the US, due to the flexibility of remote work and other reasons, or because populations were impacted by the coronavirus pandemic.

The Census Bureau published population estimates on Thursday for counties, metro areas, and micro areas.

According to the Bureau's press release, a large share — more than 73% — of counties saw natural decrease, meaning more deaths than births, in 2021. That's higher than the 55.5% in 2020.

"In 2021, fewer births, an aging population and increased mortality — intensified by the COVID-19 pandemic — contributed to a rise in natural decrease," the Census Bureau wrote in a press release.

Insider looked at new population data for the 3,143 counties and county equivalents in the US to see just how populations have changed across the US over a year. The above map shows percent changes in population size from July 1, 2020 to July 1, 2021. You can hover over the map to see what the populations for each county were for these two years and to see how the population size has changed.

Four counties in Texas, including Kaufman County, saw the largest percent increases among counties with a population of at least 20,000.

Here are the 10 large counties that saw the biggest percent increases over a year:

Not all counties saw populations grow between 2020 and 2021. New York County, which encompasses the borough of Manhattan in New York City, has a population of over 1 million and saw a population loss of over 110,000 from July 1, 2020 to July 1, 2021. A press release from the Census Bureau noted that New York County saw the second largest net domestic migration loss, meaning more people moving away to other counties in the US than moving in, right after Los Angeles County, California.

Here are the 10 large counties that saw the biggest percent declines in their populations: