What determines House representation?

Representation in the U.S. House of Representatives is determined by state population, with each state's allocation of the 435 seats recalculated after each ten-year census. The Constitution, in Article I, Section 2, requires that representatives be apportioned among the states according to their respective numbers, and that an actual enumeration be made every ten years. The total number of House seats has been capped at 435 since 1929 by the Permanent Apportionment Act, so each state's share rises or falls relative to other states based on population growth.

After every census, the Census Bureau reports population totals to the President, who then transmits them to Congress. A mathematical formula known as the method of equal proportions is used to divide the 435 seats among the states. Every state is guaranteed at least one representative, even if its population is too small to qualify mathematically. Wyoming, Vermont, and Alaska are among the states currently with only one at-large representative. Texas, with two extra seats, was the biggest beneficiary of the 2020 reapportionment, while Colorado, Florida, Montana, North Carolina, and Oregon each added one. Seat losses fell on California, Illinois, Michigan, New York, Ohio, Pennsylvania, and West Virginia, with one seat lost in each.

After apportionment, each state must redraw its congressional district boundaries to reflect the new seat allocation and population shifts within the state. This process is called redistricting and is controlled by state legislatures in most states, though some states use independent commissions. Redistricting decisions can have major political consequences, since the way district lines are drawn determines which voters are grouped together.

The link between population and House representation reflects the framers' commitment to representative democracy in the lower chamber. The framers wanted the House to be the people's chamber, with representation based on actual numbers of citizens rather than equal state representation. Equal state representation was reserved for the Senate, where each state has two senators regardless of population.

Originally, enslaved persons were counted as three-fifths of a person for purposes of apportionment under the original Constitution, a deeply unjust compromise that gave slave states extra political power. The 14th Amendment, ratified in 1868, eliminated the three-fifths clause and required that representation be based on the whole number of persons in each state. The amendment also reduced representation for states that denied the vote to adult male citizens, though this provision was never enforced.

The current cap of 435 means that some growing states have districts with fewer than 800,000 residents while others approach 1 million.