In Dale City last year, state police were brought in to evict people from homeless camps along I-95. (Jahi Chikwendiu/The Washington Post)

The study also found that Northern Virginia still needs almost 100,000 jobs to return to the employment levels reached before the recession, and that the region is home to more than one in four unemployed Virginians, far higher than any other region.

The Commonwealth Institute is an independent group with a focus on the economic issues facing low- and moderate-income residents of Virginia. In a conference call with reporters Tuesday morning, Institute President Michael Cassidy said the median income of the lowest 20 percent of households dropped 10.5 percent in real terms in four years, while the the highest income households dropped only 3 percent.

“We see not only a harder hit on household income for lower income persons,” Cassidy said, “but growing income inequality in the region,” defined as Arlington, Fairfax, Fauquier, Loudoun, Prince William, Spotsylvania and Stafford counties and Alexandria. Where the top 10 percent of NoVa households brought in 7.61 times the bottom 10 percent in 2007, the Institute found that the top 10 percent now makes 8.25 times what the bottom 10 percent makes.

The institute studied recent data from both the Census Bureau and the Bureau of Labor Statistics. Stafford cited the “substantial job shortfall” of 100,000 jobs needed to match the growing population and lost jobs since 2007 as one reason why the poor were hurt disproportionately by the recession.

“You had very significant job losses in the construction industry,” Cassidy said, “as well as tourism, leisure and hospitality and transportation. Really deep losses in sectors which tend to have larger numbers of lower wage employees.” Almost one in four construction industry jobs that existed in 2007 had disappeared from Northern Virginia by 2011, the Institute found.

Other interesting findings from the study:

■ As of 2010, there were twice as many unemployed workers in Fairfax County, about 26,000, as any other locality in Virginia.

■ There remains “substantial variation” between counties in the difference between what women and men earn. In Loudoun, with the highest median income in the country, women earn roughly 56 cents for every dollar earned by men, the lowest ratio in NoVa. Arlington had the highest ratio, with women earning 81 cents for every male dollar. Regionwide, the ratio was 71 cents for women.

■ The number of Northern Virginians living below the poverty level is ’’substantial,” the report found. And the poverty level is an income of $22,000 a year for a family of four. In Virginia, 11.1 percent of the population lives below that level. In NoVa, all jurisdictions are below that average, though Alexandria comes close with 9.9 percent below the poverty line. Loudoun had the lowest, at 3.5 percent.

■ Still, Fairfax had 62,278 individuals living in poverty in 2010, the report found, which is more poor folks than any other locality in the state. Fairfax has the most people in the state, period, so that’s not necessarily surprising, except that it’s the second wealthiest county in America. Richmond, a city, had 11,992 people living in poverty in 2010.

■ Since 2007, Northern Virginia has seen a 131 percent increase in the number of people receiving help from the Supplemental Nutrition Assistance Program. Statewide the number increased by 77 percent.

■ Similarly, families needing government help jumped more in Northern Virginia than elsewhere. The number of people using Temporary Assistance for Needy Families jumped 16 percent in NoVa, but only seven percent statewide.

■ Transportation costs hurt those who are working when they have long commutes for work. The report noted that there are exactly the same number of jobs as residents in Alexandria and Fairfax, but in Prince William, Stafford and Spotsylvania there are about twice as many workers as there are jobs. That means they are leaving the county to work, and paying to do so.

“Declining income and rising costs mean that workers and families are having a harder time making ends meet,” the Institute’s report concluded, “and these forces hit moderate and low-income Virginians the hardest.”

The full report, called Under Pressure: The State of Working Northern Virginia, is here.