Apportionment is the process of dividing the 435 seats in the U.S. House of Representatives among the 50 states based on population. It matters because House seats help determine how much voting power each state has in Congress. The process also affects presidential elections because each state's electoral votes are based on its number of House seats plus two senators.
A national count, the census, makes this system update on a regular schedule.
Every 10 years, the census counts the population of each state, and those totals are used to redistribute House seats. Each state is guaranteed at least one representative, and the remaining seats are assigned using a mathematical formula called the method of equal proportions. When population grows faster in one state than another, seats can shift from slower-growing states to faster-growing states.
This redistribution is called reapportionment, and states may then redraw district boundaries through redistricting.
Key Facts
- The U.S. House of Representatives has 435 voting seats.
- Apportionment happens every 10 years after the national census.
- Each state is guaranteed at least 1 House seat, no matter its population.
- A state's electoral votes = House seats + 2 senators.
- Reapportionment can cause states to gain, lose, or keep the same number of House seats.
- Average district population = state population ÷ number of House seats.
Vocabulary
- Apportionment
- Apportionment is the process of dividing House of Representatives seats among the states based on population.
- Census
- The census is the official national population count conducted every 10 years by the federal government.
- Reapportionment
- Reapportionment is the redistribution of House seats among states after a new census.
- Congressional district
- A congressional district is a geographic area within a state that elects one member to the U.S. House of Representatives.
- Redistricting
- Redistricting is the process of redrawing congressional district boundaries within a state after population changes.
Common Mistakes to Avoid
- Confusing apportionment with redistricting. Apportionment divides seats among states, while redistricting draws the district lines inside a state.
- Assuming every state gets House seats in exact proportion to population. This is wrong because every state must get at least one seat and the total number of voting seats is fixed at 435.
- Thinking the Senate is apportioned by population. This is wrong because every state has exactly 2 senators regardless of population.
- Forgetting that population changes are relative. A state can gain people but still lose a House seat if other states grow much faster.
Practice Questions
- 1 A state has a population of 8,400,000 and 12 House seats. What is the average population per congressional district?
- 2 State A has 18 House seats and State B has 7 House seats. How many electoral votes does each state have, and how many more electoral votes does State A have than State B?
- 3 Two states both gained population after the census, but one gained a House seat and the other lost one. Explain how this can happen under reapportionment.