Apportionment and the US Census

Fairly Representing Each States in Congress

Members of the US House of Representative voting
US House of Representatives Votes To Elect A New Speaker. Chip Somodevilla / Getty Images

Apportionment is the process of fairly dividing the 435 seats in the U.S. House of Representatives among the 50 states based on population counts from the decennial U.S. census. Apportionment does not apply to the U.S. Senate, which under Article I, Section 3 of the U.S. Constitution, is comprised of two senators from each state. 

Who Came Up With the Apportionment Process?

America’s Founding Fathers wanted the House of Representatives to represent the people rather than the state legislatures, which are represented in the Senate. To that end, Article I, Section II of the Constitution provides each state shall have at least one U.S. Representative, with the total size of a state’s delegation to the House based on its total population. Based on the national population as estimated in 1787, each member of the House in the First Federal Congress (1789–1791) represented 30,000 citizens. As the nation grew in geographic size and population, the number of representatives and the number of people they represented in the House increased accordingly..

Conducted in 1790, the first U.S, Census counted 4 million Americans. Based on that count, the total number of members elected to the House of Representatives grew from the original 65 to 106. The current membership of the House of Representatives was set at 435 by the Reapportionment Act of 1929, which established a permanent method for apportioning a constant number of seats according to each decennial census.

How is Appropriation Calculated?

The exact formula used for apportionment was created by mathematicians and politicians and adopted by Congress in 1941 as the "Equal Proportions" formula (Title 2, Section 2a, U. S. Code). First, each state is assigned one seat. Then, the remaining 385 seats are distributed using a formula that computes "priority values" based on each state's apportionment population.

Who is Included in the Apportionment Population Count?

The apportionment calculation is based on the total resident population (citizen and noncitizen) of the 50 states. The apportionment population also includes U.S. Armed Forces personnel and federal civilian employees stationed outside the United States (and their dependents living with them) who can be allocated, based on administrative records, back to a home state.

Are Children Under 18 Included?

Yes. Being registered to vote or voting is not a requirement to be included in the apportionment population counts.

Who is NOT Included in the Apportionment Population Count?

The populations of the District of Columbia, Puerto Rico, and the U.S. Island Areas are excluded from the apportionment population because they do not have voting seats in the U.S. House of Representatives.

What is the Legal Mandate for Apportionment?

Article I, Section 2, of the U.S. Constitution mandates that an apportionment of representatives among the states be carried out each 10-year period.

Schedule for Reporting and Applying Apportionment Counts

According federal law codified in Title 13 of the U.S. Code, the Census Bureau must deliver the apportionment counts—the census-counted resident population totals for each state—to the Office of the President of the United States within nine months of the official census date. Since the 1930 census, the census date has been April 1, meaning the Office of the President must receive the state population counts by December 31 of the census year. 

To Congress

According to Title 2, U.S. Code, within one week of the opening of the next session of Congress in the new year, the president must report to the Clerk of the U.S. House of Representatives the apportionment population counts for each state and the number of representatives to which each state is entitled.

To the States

According to Title 2, U.S. Code, within 15 days of receiving the apportionment population counts from the president, the Clerk of the House of Representatives must inform each state governor of the number of representatives to which that state is entitled.

Using its population count and more detailed demographic results from the census, each state legislature then defines the geographic boundaries of its congressional and state election districts through a process known as redistricting