The yearly ACS population estimates aren’t accurate — especially for urban regions in the Northeast and Midwest — and the Census site literally says the numbers should not be used as a hard measure of total population.

As others noted, these estimates showed New Jersey losing population every year between 2010 and 2019, and then the 2020 Census proved those wrong since we actually grew in population so much that we almost gained a new congressional district.

Some helpful context here: https://twitter.com/urbanjerseyguy/status/1641483265960816642?s=46&t=omy7Z1bk_04sxcMT7dPLIg