For decades, a cliché about California was that the weather was always sunny and mild during Pasadena’s Rose Bowl Parade on New Year’s Day, and snowbound television viewers in other states were thus enticed to migrate westward.

The cliché had a kernel of fact. California did experience very strong population growth during the latter years of the 20th century due to post-World War II flows of people from other states and later from other nations. The domestic and foreign migrants tended to be young, so their impact was magnified by increases in births.

During the 1980s alone, the combined effects of a strong economy, a tidal wave of mostly foreign immigration and a baby boom added six million souls to California.

Population growth slowed markedly during the 1990s, thanks largely to out-migration after Southern California’s aerospace/defense industry collapsed, then dropped to a relative trickle. It was as if someone flipped a switch as California entered the 21st century.

Births are declining, deaths are increasing (and not just because of COVID-19), we lose more people to other states than we gain, and foreign immigration is scant.

New Census Bureau estimates, released in late December, reveal that California actually saw a population loss in the year that ended on July 1 of about 69,000 residents, which translates into just a 5.7% gain since the 2010 census, much lower than the nation as a whole.

California’s demographers don’t agree. A few days earlier, the state Department of Finance released its own numbers for the year ending on July 1, showing a gain of 21,200.

In a state as large as California, a 90,200-person differential is tiny. However, over the last decade, ever since the 2010 census, the gap between the two agencies’ calculations has become fairly wide.

The Census Bureau says that on July 1, California had 39.37 million people while the Department of Finance pegged it at 39.78 million, a difference of about 400,000. During the previous decade their annual estimates had differed by as much as a million and the 2010 census settled the issue, largely in favor of the Census Bureau.

The 2020 census will settle it again, but no matter how you slice it, California’s 170 years of strong population growth have ended and we may have joined other states in the Northeast and upper Midwest whose populations have declined.

California gained just one congressional seat after the 2000 census, saw no gain after the 2010 census for the first time and is now poised to lose at least one seat and perhaps even two.

There’s much more to California’s demographic flip than congressional seats, however.

For one thing, a stagnant or declining population means we have a state that’s tilting generationally, with the elderly making up a rapidly growing cohort. That, in turn, means a smaller number of potential workers, a declining number of children and thus declining student enrollments. It also means fewer customers for retail businesses and, potentially, less pressure to build more housing, fewer cars on the road and other economic impacts.

All of these effects obviously will have policy and political ramifications. Not only will California have to adjust to having fewer members of Congress, for example, but within the state we will see shifts of political representation, largely from coastal communities which are seeing little or no growth to inland regions that are still growing, albeit slowly. That shift will become clearer when legislative and congressional districts are redrawn by the state’s redistricting commission this year.

Dan Walters is a CalMatters columnist.