The Census Bureau last week released county and city populations for the last of the 50 states from the 2010 Census last week, ahead of schedule. Behind the columns of numbers are many vivid stories of how our nation has been changing -- and some lessons for public policy, as well. Geographically, our population is moving to the south and west, to the point that the center of the nation's population has moved to Texas County, Missouri. That sounds like the familiar story of people moving from the Snow Belt to the Sun Belt, but that's not exactly what's happening....