Historian James N. Gregory examined Census Bureau statistics and other records to learn more about the migrants. Based on a 1939 survey of occupation by the Bureau of Agricultural Economics of about 116,000 families who arrived in California in the 1930s, he learned that only 43 percent of southwesterners were doing farm work immediately before they migrated. Nearly one-third of all migrants were professional or white-collar workers. The poor economy displaced more than just farmers as refugees to California; many teachers, lawyers, and small business owners moved west with their families during this time. After the Great Depression ended, some moved back to their original states. Many others remained where they had resettled. About one-eighth of California's population is of Okie heritage.