According to the U.S. Census Bureau, California's population surpassed 38.3 million as of July 2013. California gained slightly more than 332,000 residents from July 2012 to July 2013; this is the largest annual increase since 2004. The current population estimate is a million higher than the 2010 Census figure. The state’s population is projected to reach 47.7 million in 2040.
California’s population growth has slowed from the high-growth decades of the 1970s and 1980s, when the rates were 18.7% and 26% respectively. Annual growth rates in California are expected to fluctuate between 0.9% and 0.8% until 2035.
There are two different estimates of California’s population, based on two different estimates of net domestic migration—the number of people moving to the state from elsewhere in the U.S minus the number of people leaving the state. The California Department of Finance’s population estimate is used by state agencies for programing and planning. The Census Bureau’s estimate is used nationally and for some allocations of federal funds.
Between 2011 and 2012 California’s population grew 0.95%. Growth varied widely across California: 19 counties, most of them in the northern part of the state, registered declines. Declines were greatest in Lassen County and Modoc County (both were down 1.8%).
The most populous counties showed growth rates above the state average; Los Angeles County was an exception, with a growth rate of 0.75%. Four counties in the Bay Area (Alameda, San Francisco, Santa Clara, and San Mateo) registered the highest population growth among California counties (between 1.5% and 1.4%).
Between 2012 and 2013 California added 332,166 people. The state gained 169,266 residents due to net foreign immigration (more people arriving than leaving) but lost about 102,972 residents due to net domestic migration (more people leaving than arriving). This amounts to a net migration loss of 66,294 people. Natural increase—births minus deaths—made up for this loss and then some, adding 265,872 people. California's net domestic migration has been negative for most of the last two decades.