Congressional apportionment is the process, run every ten years, that divides the 435 seats in the U.S. House of Representatives among the 50 states according to their populations as measured by the decennial census. Because the total number of seats is fixed by law, a state’s gain is always another state’s loss. The same calculation also determines each state’s Electoral College votes and shapes how hundreds of billions of federal dollars are distributed.
Where the Rule Comes From
Article I, Section 2 of the Constitution directs that Representatives “be apportioned among the several States according to their respective Numbers” and guarantees every state at least one Representative regardless of size.1Constitution Annotated. Article I, Section 2 The Fourteenth Amendment updated the counting rule, replacing the original three-fifths clause with a straightforward instruction to count “the whole number of persons in each State.”
The Constitution does not set the size of the House. Congress did that by statute. The Permanent Apportionment Act of 1929, now codified at 2 U.S.C. ยง 2a, fixed the number of Representatives at 435, set out the mathematical formula, and required the President to transmit the resulting figures to Congress after each census.2Office of the Law Revision Counsel. 2 USC 2a – Reapportionment of Representatives That cap has held while the country has more than tripled in population, so each district now represents roughly 761,169 people on average, based on the 2020 census.3U.S. Census Bureau. Apportionment of Seats in the U.S. House of Representatives
The Census Count Behind the Numbers
Every reapportionment starts with the decennial census, conducted on April 1 of years ending in zero. Federal law requires the Secretary of Commerce to complete the population tabulation within nine months and report the results to the President.4Office of the Law Revision Counsel. 13 USC 141 – Population and Other Census Information
The count reaches every person living in a state, not just citizens or voters. Lawful permanent residents, undocumented immigrants, and children all factor into a state’s total, consistent with the Fourteenth Amendment’s instruction to count “the whole number of persons.”5Constitution Annotated. Fourteenth Amendment, Section 2 Military and federal civilian employees stationed overseas, along with their dependents, are assigned back to their home state using administrative records.6U.S. Census Bureau. 2020 Census Overseas Population Counts
Residents of Puerto Rico, Guam, the U.S. Virgin Islands, and the other U.S. territories are not counted toward any state and do not affect the apportionment. Those territories send non-voting delegates to the House instead.
How the 435 Seats Get Divided: The Method of Equal Proportions
The formula Congress uses is called the Method of Equal Proportions, adopted after the 1940 census.7U.S. Census Bureau. Computing Apportionment Its aim is to make each state’s share of House seats track its share of the national population as closely as possible, minimizing the percentage gap in district size between any pair of states.
The math runs in two stages. First, each of the 50 states gets its constitutionally guaranteed one seat. That uses up 50 of the 435. The remaining 385 seats are then awarded one at a time. Each state’s population is divided by a series of mathematical divisors to produce “priority values,” and the state with the highest priority value takes the next seat. The list is recalculated after every assignment, and the process continues until all 435 seats are gone.7U.S. Census Bureau. Computing Apportionment
Once the calculation is complete, the President sends Congress a statement showing each state’s new seat count. The Clerk of the House then has fifteen calendar days to send each governor a certificate of the state’s entitlement.2Office of the Law Revision Counsel. 2 USC 2a – Reapportionment of Representatives
Which States Gained and Lost After the 2020 Census
Because the total is capped at 435, apportionment is zero-sum. A state does not need to shrink to lose a seat. It just needs to grow more slowly than the states pulling ahead.
The 2020 reapportionment produced these shifts:8U.S. Census Bureau. 2020 Census Apportionment Results Delivered to the President
- Texas gained two seats.
- Colorado, Florida, Montana, North Carolina, and Oregon each gained one seat.
- California, Illinois, Michigan, New York, Ohio, Pennsylvania, and West Virginia each lost one seat.
California lost a House seat for the first time in its history, not because it shrank but because it grew more slowly than states in the Sun Belt and Mountain West. The overall pattern reflected a decade of migration toward those regions and away from parts of the Midwest, Northeast, and Appalachia.
Effect on the Electoral College
A state’s Electoral College weight moves with its House delegation. Each state gets electors equal to its Representatives plus its two Senators.9National Archives. Distribution of Electoral Votes When apportionment changes a state’s House count, its electoral vote count changes by the same number.
The smallest states, with a single Representative, hold three electoral votes. Washington, D.C., under the Twenty-Third Amendment, receives electors equal to what it would get if it were a state, capped at the total held by the least populous state, which in practice is three.10Constitution Annotated. Twenty-Third Amendment, District of Columbia Electors The national total is 538: the 435 House seats, 100 Senators, and D.C.’s three.
The shifts from the 2020 census first showed up in the 2024 presidential election and will apply again in 2028. The next reapportionment, from the 2030 census, will reshape the electoral map beginning with the 2032 election.
Apportionment Is Not Redistricting
Apportionment sets how many districts a state gets. Redistricting is the separate process of drawing the district lines on a map. Any state that gains or loses a seat has to redraw its boundaries so districts contain roughly equal populations, and most states redraw even when their seat count is unchanged, to account for internal population shifts. Depending on the state, the legislature or an independent commission handles the drawing.
Federal law does provide interim rules when a state has not finished redistricting in time for an election. Additional Representatives from a state that gained seats are elected at-large, and a state that lost seats but still has the old number of districts elects from those existing districts.2Office of the Law Revision Counsel. 2 USC 2a – Reapportionment of Representatives These fallbacks rarely come into play because states almost always complete new maps before the next election.
Why the Count Also Moves Federal Dollars
The same census figures that drive apportionment steer more than $2.8 trillion in annual federal funding across at least 353 assistance programs, including Medicaid, Medicare, SNAP, highway construction grants, and Supplemental Security Income.11U.S. Census Bureau. The Currency of Our Data: A Critical Input Into Federal Funding Medicaid alone distributed over $568 billion in fiscal year 2021 using formulas tied to census population data. An undercount in a given state does not only cost that state a House seat. It can reduce federal funding for hospitals, roads, and schools for the full decade until the next count.