Census Bureau

Congressional Apportionment--How it's Calculated

The Constitution provides that each state will have a minimum of one member in the House of Representatives, and the current size of the House (435 seats) has not changed since the apportionment following the 1910 census. Thus, the apportionment calculation for Census 2000 will divide 385 seats among the 50 states. Congress decides the method used to calculate the apportionment.

The method for calculating the apportionment has changed over time. The methods used through most of this century have been based upon the use of a mathematically determined priority listing of states. Adopted by congress in 1941 and used through the 1990 census, the method of equal proportions also results in a listing of the states according to a priority value--calculated by dividing the population of each state by the geometric mean of its current and next seats--that assigns seats 51 through 435. This will be the method used in Census 2000, according to provisions of Title 2, U.S. Code.

For a technical description of how the method of equal proportions was used in developing the 1990 apportionment counts, see Computing Apportionment.

Go to: "Delivering the numbers"
Go to: "Congressional Apportionment main page"