 As of 2006, California had an estimated population of 37,172,015, more than 12 percent of the U.S. population.This includes a natural increase since the last census of 1,557,112 people (i.e., 2,781,539 births minus 1,224,427 deaths) and an increase due to net migration of 751,419 people.Immigration resulted in a net increase of 1,415,879 people, and migration from within the U.S. resulted in a net decrease of 564,100 people.