Loudoun County's well-heeled households keep getting richer while gentrification is boosting incomes in the District even as the region's other households are faltering in the post-recession era.

Loudoun added to its lead as the richest county in the region as median household incomes reached nearly $120,000 in 2010, for an 8 percent increase over 2008, according to the U.S. Census Bureau. Meanwhile, Loudoun's nearest competitors -- Fairfax and Howard counties -- are losing ground as median household incomes there stayed flat.

In the District, median household incomes also increased roughly 8 percent in two years to nearly $61,000, in a boost demographers say is the result of a growing young professional population and development boom.

Loudoun widens lead
By rank2000 Income2-year change5-year change10-year change2010 change
Loudoun County$80,6488.0%21.4%48.2%$119,540
Fairfax County$83,570-3.5%8.9%23.3%$103,010
Howard County$74,1670.1%11.6%37.2%$101,771
Arlington County$63,001-1.5%18.1%50.8%$94,986
Prince William County$67,0494.5%13.1%38.2%$92,655
Montgomery County$71,173-5.2%8.5%25.3%$89,155
Prince George's County$55,192-1.7%10.5%26.9%$70,019
Source: U.S. Census Burea

In the suburbs, Loudoun's success is attributed to its ability to draw higher-skilled workers like engineers and its high-end housing stock -- even after the housing crisis bottomed out the economy in late 2008.

"[In 2007 and 2008], those buyers who were available in the market would have been looking for bargains," said Anirban Basu, CEO of Sage Policy Group in Baltimore. "Because Loudoun County was so heavily impacted by the foreclosure crisis, it may be that many of the best bargains emerged there, allowing Loudoun County to continue to expand meaningfully."

That's also impacted Prince William County, the only other jurisdiction to see a two-year gain. Recently the county has seen a growth rate to rival Loudoun's, and incomes there have increased by 4.5 percent.

Meanwhile D.C.'s cushion from the recession thanks to federal jobs made it a draw for college graduates. And as the cost of living grows, lower-income families are leaving the city.

In fact, over the last five years of the decade, just Loudoun and the District matched or increased their gains from the first five years.

In contrast, most counties saw big gains over the first half of the decade and slid back in the last few years of the 2000s. But it's not as clear-cut as it seems, said Lisa Sturtevant, assistant research professor at George Mason University's Center for Regional Analysis.

"It's not that the existing residents are getting worse-off, it's that the source of the population growth has somewhat lower incomes," she said.

In Montgomery, Fairfax and Prince George's counties, minorities are driving nearly all the population growth. From 2005 to 2010, incomes in those counties increased between 8 and 11 percent, marking the lowest gains in the region.

That's largely a product of jobs, as Sturtevant noted Montgomery has seen growth in lower-paying jobs in the service industry and in educational services while Northern Virginia has seen growth in technology and engineering.