After the increased border security following the 9-11 attacks in 2001, the back-and-forth pattern became dangerous. People kept coming north, but they stayed in the U.S. and sent money home every month. Locked into the American economy year-round, millions of these undocumented workers moved out of season agricultural jobs into year-round jobs in restaurants, hotels, construction, landscaping and semiskilled factory work, such as meatpacking. Most paid federal social security taxes into imaginary accounts (and thus were not eligible for benefits.) Few had high enough incomes to pay federal or state income taxes, but all paid local and state sales taxes on their purchases as well as local property taxes (via their rent payments to landlords). By 2007 there were 12  million or so undocumented workers in the U.S.