Virginia, Florida and Nevada had the most significant declines in their populations of illegal immigrants. The large declines in Florida and Nevada were probably due to the housing crisis and the loss of thousands of construction jobs, which immigrants often fill, experts said. Florida's illegal immigrant population fell by 375,000, to an estimated 675,000, between 2008 and 2009, and Nevada's decreased by 50,000 to an estimated 180,000 during that period.