Via Invasive Exotic Species, here's a Census Bureau graph of top ten net flows between California and other American states in 1955-1960 (red) and 1995-2000 (blue). In the later 1950s, all the net flows were toward California. In the later 1990s, all the net flows were out of the Golden State, except for a thin influx from New York, probably to work in then-booming Silicon Valley and Hollywood.

And yet, the total population of California grew by over 2 million from 1995 to 2000.