Population shifts mean five states that voted for Joe Biden will lose seats in the House when congressional districts are redrawn later this year, new Census numbers released Monday show, but will gain seats in two other states. Only twoTrump-voting states will lose a seat.

Why it matters: Apportionment and redistricting — the process of redistributing political power among and within the states— comes as Democrats hold slim majorities in both congressional chambers and Republicans have a strong grip on the process of re-drawing district lines.

By the numbers: California — the nation's most populous state — is losing a seat for the first time in history.

• Other states losing one:Illinois, Michigan, New York, Ohio, Pennsylvania and West Virginia.
• The shifting — but still very red — state of Texas will pick up two of the reapportioned seats. Colorado, Florida, Montana, North Carolina and Oregon will also gain one seat each.

What they're saying: Although Biden states will lose out during this round of apportionment, Brookings Institution demographer William Frey told Axios the overall gains in western states and Texas reflect, at least in part, people moving out of one Democrat-leaning state: California.

• So, "politically, many of these Electoral College-seat gaining states may be trending 'bluer' politically because of the movement into them from Democratic-leaning states," he said.

Between the lines: Apportionment, which happens every ten years, is the process of dividing up the 435 House seats according to the latest population counts for each state. That's measured by the Census, held the first year of each decade.

• The full Census data that will be used for redistricting — the process of drawing new electoral districts in states — will not be publicly released until the end of September.
• The delay was caused by the coronavirus and the Trump administration's attempts to exclude unauthorized immigrants from the Census count, which they believed would benefit Democrats.

Democrats are bracing for GOP-friendly district lines, since Republicans have unified control of the congressional redistricting process in 18 states as opposed to seven for the Democrats, according to the Brennan Center.

• "Redistricting could likely determine who controls the House of Representatives in 2022, but also going into the next decade," Stanford Law School's Nate Persily, a redistricting expert, told Axios.

The big picture: The newly released data also underscores America's slowed growth and aging population, according to Frey.

• The stagnating population growth, in small part due to the pandemic, means the U.S. should take "a serious look at our immigration policy going forward," he said.
• Utah was the fastest growing state. Three states lost populations, with West Virginia's population declining at the fastest rate.