Demographers call the trend a natural decrease.
"In all, roughly 760 of the nation's 3,142 counties are fading away, stretching from industrial areas near Pittsburgh and Cleveland to the vineyards outside San Francisco to the rural areas of east Texas and the Great Plains. Once-booming housing areas, such as retirement communities in Florida, have not been immune.
West Virginia was the first to experience natural decrease statewide over the last decade, with Maine, Pennsylvania and Vermont close to following suit, according to the latest census figures. As a nation, the U.S. population grew by just 9.7 percent since 2000, the lowest decennial rate since the Great Depression."