Seven of nation’s 10 most affluent counties are in Washington region

The Washington region has emerged from the recession looking even more affluent compared with the rest of the country, boasting seven of the 10 counties with the highest household incomes in the nation, new census numbers show.

With a median household income surpassing $119,000, Loudoun County heads the list. Fairfax County, at nearly $106,000, is second. Both have held the same positions for several years running.

More surprising, Arlington County leapfrogged from the fifth spot to third, with a median household income of almost $101,000, a $6,000 gain in one year. Four in 10 households in the county are single person, leaving Arlington with a relatively small share of residents whose affluence comes from two incomes, compared with Loudoun and Fairfax.

Other counties in the top 10 are Howard, Prince William, Fauquier and Montgomery, which had dropped out of it in 2010. Among states, Maryland has the nation’s highest household income level, and Virginia is ninth.

The rankings in the 2011 American Community Survey released Thursday expand Washington’s dominance among high-income households, reflecting a regional economy that was largely cushioned as the recession yanked down income levels elsewhere. Household incomes rose in most counties around Washington last year, even as they continued to sink around the country.

The stability of an economy built on the pillars of the federal government, its legions of contractors and a flourishing high-tech sector is evident in the income rankings.

In 2007, before the recession began, five counties in suburban Washington made it into the top 10. By 2010, there were six. The seven in the latest ranking is an all-time high.

“It’s not only that we have low unemployment and a lot of dual-income households,” said Stephen Fuller, director of the Center for Regional Analysis at George Mason University. “We lost a few government jobs, but not the high-paying, professional business-service jobs that are still growing, if not as fast as they used to. Since the rest of the country is in such poor shape, we just have to show a little bit of growth here, and we look pretty good.”

While looming federal budget cuts could threaten the growth of Washington’s high-income households, the region is rife with the kind of residents that have thrived even in tough times.

The area has the nation’s highest level of adults with college degrees. It also is high in shares of households that have two incomes and married couples who postpone having children until they establish themselves professionally.

“A big sliver of American society that generally does well tends to cluster in Washington,” said William Frey, a demographer with the Brookings Institution. “When people make the argument that $250,000 is middle income, that’s way higher than most of the country regards as middle income. But here in Washington, your next-door neighbor has that kind of income.”

The census rankings are estimates based on incomes reported by a sample of people who receive the American Community Survey, which replaced the old long-form census questionnaire. The margins of error can be as high as 14.5 percentage points in a smaller county like Fauquier or as low as 2.5 percentage points in a large county like Fairfax.