Hugh Pickens writes "The Washington Post reports that the U.S. birthrate is at its lowest since 1920, the earliest year with reliable records. The rate decreased to 63.2 births per 1,000 women of childbearing age — a little more than half of its peak, which was in 1957. The overall birthrate decreased by 8 percent between 2007 and 2010, but the decline is being led by immigrant women hit hard by the recession, with a much bigger drop of 14 percent among foreign-born women. Overall, the average number of children a U.S. woman is predicted to have in her lifetime is 1.9, slightly less than the 2.1 children required to maintain current population levels. Although the declining U.S. birthrate has not created the kind of stark imbalances found in graying countries such as Japan or Italy, it should serve as a wake-up call for policymakers, says Roberto Suro, a professor of public policy at the University of Southern California. 'We've been assuming that when the baby-boomer population gets most expensive, that there are going to be immigrants and their children who are going to be paying into [programs for the elderly], but in the wake of what's happened in the last five years, we have to reexamine those assumptions,' he said. 'When you think of things like the solvency of Social Security, for example, relatively small increases in the dependency ratio can have a huge effect.'"