We already knew that, beginning roughly with the start of the financial crisis, the metro D.C. area was gaining in prominence relative to other big American cities. D.C. suburbs now make up six of the 10 richest counties in America, including the top three.
New Census data shows that the D.C. area has grown faster than anywhere else in the past decade. Three D.C. suburbs, led by Arlington County, were among the four municipalities showing the greatest income gains over the period measured between Censuses, 2000-2009. The median household income in Arlington County increased $12,705 in that timespan.