"Essentially all of the fastest-growing districts are in inland areas south of the Mason-Dixon line, or are west of the Continental Divide. Many are in areas that demographers describe as ‘exurbs’: newly developing areas that are located relatively far — perhaps a 30- or 60-minute drive — from cities like Phoenix, Dallas, Houston, Las Vegas, Charlotte or Atlanta, and that attract an upscale mix of commuters, families and retirees."