Every 10 years, the 435 seats in the U.S. House of Representatives are re-allocated among the states according to updated population counts in the national census in a process called apportionment.

Every state, no matter how small, gets one seat; thereafter, additional seats are assigned according to a formula that guarantees that each congressperson represents a similar number of constituents in each state. That means that larger, fast-growing states like Texas and California are likely to gain seats at the expense of smaller states and states with slower population growth.

Apportionment doesn’t merely affect representation in Congress: it also affects how many electoral votes each state gets in the presidential elections (which is equal to the total size of each state’s congressional delegation, including two senators from each state).

Explore what it takes to change the balance of power in Washington. Adjust the sliders below to see how different patterns of population growth among the states will affect apportionment in 2020:

Maine rust belt scenario
‘Border wall’ scenario
‘Independence Day’ scenario
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Projected congressional seats by state in 2020

based on 2010-2015 population growth trends
SOURCE: U.S. Census Bureau
INTERACTIVE: Christian MilNeil | @vigorousnorth