“You will know that California has truly crossed a line when home prices start falling,” Christopher Thornberg, founding partner of Beacon Economics, a consulting firm in Los Angeles, told me late last year.

And, well, home prices have done the opposite.

More recently — and particularly during the Trump administration — immigration slowed significantly. Immigration represented between 0.4 and 0.5 percent of California’s annual population increase through the first half of the decade, H.D. Palmer, a spokesman for the state’s Department of Finance, told Shawn. But starting in 2017, when President Donald J. Trump took office, that began to decline, to less than 0.1 percent last year.

If California is still growing, why is it going to lose a congressional seat?

As Eric McGhee, a political participation expert with the Public Policy Institute of California, explained early last year: “It’s a zero-sum game.”

Although for much of American history, seats were added freely to the House of Representatives, in 1911, the number was capped at 435.

Which means that your state can grow and still lose representation, if it doesn’t grow enough relative to other states.

In 2011, California’s number of representatives stayed flat for the first time, at 53. And while there were concerns about participation in the census last year for a host of reasons, demographers were already forecasting that the state could lose a seat.

What happens next?

Broadly, the shifts will redistribute political power across the country — although it remains to be seen what that will look like.