Apportionment

The Constitution requires that House seats be apportioned among the states according to population, counted every ten years, with each state guaranteed at least one representative. The original text counted enslaved people as three fifths of a person, a formula the Fourteenth Amendment replaced in 1868 with the whole number of persons in each state. Apportionment also sets each state's electoral votes, since a state's electors equal its House seats plus two.

The House grew with the country until 1911, when it was fixed at 435 members. After Congress failed to reapportion following the 1920 census, the Permanent Apportionment Act of 1929 made the process automatic: after each census the President transmits the new distribution to Congress, without a new vote. Since 1941 seats have been divided using the method of equal proportions, a formula that assigns each seat in turn to the state with the highest priority value. The average district now contains about 761,000 people, and six states have only one representative.

Apportionment shifts political power between regions. After the 2020 census, Texas gained two seats, Colorado, Florida, Montana, North Carolina, and Oregon one each, while California, Illinois, Michigan, New York, Ohio, Pennsylvania, and West Virginia each lost one. Because the House size has been fixed for over a century while the population has more than tripled, some have proposed enlarging it. Disputes have also arisen over whether noncitizens, who are counted in the census, should be excluded from the apportionment base.