According to analysis from Election Data Services (EDS), using estimates from the Census Bureau, “12 states will be impacted by changes in their congressional delegation if these new numbers were used for apportionment today.”

While there are multiple possible scenarios, EDS expects Florida and Texas to be the biggest winners and Illinois to possibly be the biggest loser. According to their report:

States Gaining Districts (6 or 7)

Arizona +1 (from 9 to 10)

Colorado +1 (from 7 to 8)

Florida +2 (from 27 to 29)

Montana even or +1 (from At-large to 2)

North Carolina +1 (from 13 to 14)

Oregon +1 (from 5 to 6)

Texas +3 (from 36 to 39)

States Losing Districts (9)

Alabama -1 (from 7 to 6)

Illinois -1 or -2 (from 18 to 17 or 16)

Michigan -1 (from 14 to 13)

Minnesota -1 or even (from 8 to 7 or none)

New York -1 (from 27 to 26)

Ohio -1 (from 16 to 15)

Pennsylvania -1 (from 18 to 17)

Rhode Island -1 (from 2 to 1)

West Virginia -1 (from 3 to 2)

California is nearing the cusp of losing a seat as well.

These estimates could be impacted not just by actual changes in population, but by the accuracy of the 2020 headcount. With a potential undercount in rural America (from a change in counting methodology and insufficient testing) and a potential undercount among the immigrant population (due to the addition of a citizenship question), these estimated outcomes for House seats could change further.

For instance, the New York Times recently tried to estimate the impact of the citizenship question with several models, suggesting that a 15 percent undercount of noncitizens would give Colorado and Montana each an extra seat, while costing New York and California one seat each, and that a headcount of only citizens would flip 10 seats (Colorado, Louisiana, Michigan, Minnesota, Missouri, Montana, and Pennsylvania would all gain a seat, while Florida, Texas and New York would each lose one seat, and California would love four seats).

EDS has a long history of reapportionment studies as well as other electoral maps and info.