In California, as we reach mid-year with the largest population that any state has ever had (about 38.5 million), we know that sometime in 2015 we’ll probably add the 40th million person, according to the Department of Finance. However, we won’t know for sure until the end of the decade when our next official census is taken. In the meantime, state and local planners have to rely on estimates.
These data come from 26 different sources, including birth and death reports (which tell us our natural increase), federal income tax reports, Medicare and military records, legal immigration, prison populations, and school enrollment.
Migration (the movement of people into, out of, and within the state) is tracked through change-of-address records from the Department of Motor Vehicles. Finally, the State Department of Finance — as well as private organizations, like the Rand Corporation — does an annual survey, usually based on city and county estimates.
Waves of immigration
Although the state’s current growth is due mainly to natural increase (the excess of births over deaths), we became the most populous state because of immigration. Before the first Europeans came to California, about 300,000 Indians inhabited the region, which was the northernmost part of Mexico, under Spanish rule...