Depends on how you look at it. California is losing residents to other states and as the population ages, but those losses are being more than offset by new births and foreign-born immigration. The number of Californians is still increasing, but our once-robust growth rate has slowed.
California added 141,300 residents between July 2018 and July 2019, bringing the state population to an estimated 39.96 million people, according to the California Department of Finance. But while foreign immigration remains high, more Californians are leaving for other states than vice versa, and have been since the 1990s. The 0.35% growth rate was also a record low.