<P> After a century, the San Joaquin Valley remains a major producer . The Kern County part of the valley in 2008 had over 42,000 producing oil wells that provided about 68% of the oil produced in California, 10% of the entire United States production, and close to 1% of the total world oil production . Add to that another producing 2,000 wells in Fresno County . If the valley were a state in its own right, it would rank behind Texas, Alaska, and Louisiana as the fourth largest oil producer state in the country . </P> <Table> <Tr> <Th_colspan="2"> (hide) California oil production in 2005 </Th> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Th> State </Th> <Th> Barrels / day </Th> </Tr> <Tr> <Th> Louisiana </Th> <Th> 1,463,000 </Th> </Tr> <Tr> <Th> Texas </Th> <Th> 1, 331000 </Th> </Tr> <Tr> <Th> Alaska </Th> <Th> 894,000 </Th> </Tr> <Tr> <Th> California San Joaquin Valley </Th> <Th> 515,000 </Th> </Tr> <Tr> <Th> Oklahoma </Th> <Th> 177,000 </Th> </Tr> <Tr> <Th> New Mexico </Th> <Th> 171,000 </Th> </Tr> </Table> <Tr> <Th_colspan="2"> (hide) California oil production in 2005 </Th> </Tr> <Tr> <Th> State </Th> <Th> Barrels / day </Th> </Tr>

What has been the largest growth industry in california over the past 20 years