

The Census is conducted every 10 years, and helps ensure that there is an accurate count of where people reside across the country and in the states.
At the federal level, the Census is used to inform the reapportionment of the 435 congressional seats in the House of Representatives ― states may gain or lose seats relative to the previous apportionment because each House district represents roughly 710,000 residents (states with a population smaller than that threshold have a single at-large district).
Similarly, the Census informs the redistricting process for state legislatures, and districts for state House & Senate seats are required to be redrawn at least once every 10 years. The apportionment and redistricting that follows the 2020 Census will take effect for congressional and state legislative districts beginning in 2022.
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