California, the most populous state in the country, had its slowest recorded growth rate in its history last year.

Estimates released Wednesday show California had 39.9 million people as of Jan. 1, adding nearly 187,000 people for a growth rate of 0.47% — the lowest since 1900, the earliest records available. State officials said they expected the state’s birth rate to decline, but they were surprised by how much: More than 18,000 fewer births than the previous year. And while thousands lost their homes after last year’s deadly wildfire in the northern part of the state, initial estimates show most people shuffled to cities closest to the blaze.

Despite the slowdown, California remains by far the country’s most populous state. Texas at No. 2 is still shy of 30 million people. The new population estimates come as the state is preparing for the 2020 national census, an important headcount used to distribute federal tax dollars and decide congressional representation.

So what might be possible factors behind the decline? We check in with demographers to explain the numbers.

With files from the Associated Press.

Guests:

Dowell Myers, demography professor at USC; director of Population Dynamics Research Group at USC; he tweets

Randall Kuhn, demographer and associate professor of community health sciences at UCLA