A street in the Anacostia neighborhood of Washington. (Marvin Joseph/The Washington Post)

Through years of growing gentrification in the nation’s capital, a question has vexed demographers and housing policymakers: When longtime D.C. residents of modest means are priced out of their neighborhoods by escalating rents and real estate taxes associated with rising property values, where exactly do they tend to go?

The information needed to precisely track these people — census data and public Internal Revenue Service records, for example — either isn’t available or is frustratingly hard to analyze, according to the researchers. So a detailed, definitive answer remains elusive.

But more and more indicators, including a recent report by the D.C. Fiscal Policy Institute, suggest that the revitalization of some city neighborhoods by affluent newcomers has a corresponding negative impact on other parts of the District, causing pockets of poverty to grow larger, especially east of the Anacostia River.

The report, by researcher Claire Zippel, who has specialized in affordable housing issues, describes increasing economic and racial segregation in Washington.

“The findings clearly suggest that because it’s become so expensive to live west of the river, a lot of longtime residents, certainly lower-income African American residents, have been pushed out of that area,” Zippel said in an interview.

“The evidence is, they are increasingly living east of the river,” in Wards 7 and 8, “where poverty and racial segregation are really, really high,” she said.

Zippel stressed that no clear cause-and-effect has been determined.

“The increasing number of people living east of the river now, we don’t know where they lived before,” she said, meaning she is uncertain whether residents dislocated by gentrification have been moving mainly to Wards 7 and 8. They could have arrived from elsewhere.

Still, the numbers are stark in a report that examines each side of the river in 2007 and in 2015, comparing demographic and economic data.

Overall from 2000 to 2015, the District’s population grew by about 100,000 people, to a total of 672,000, the first increase in half a century. In those 15 years — because of an influx of gentrifiers, mainly white professionals — the percentage of African Americans living in Washington plunged from 60 percent to slightly less than half.

The number of African Americans in the District hasn’t changed much; they simply make up a smaller percentage of a bigger total. And they are “a shrinking portion of the city west of the river,” Zippel wrote. “Just 33 percent of residents living west of the Anacostia River are black, down from 42 percent in 2007.”

The growing concentration of African Americans east of the river, compared with the rest of the city, also affects economic statistics.

“The poverty rate east of the river remained stubbornly high at 33 percent in 2015, up from 27 percent in 2007,” Zippel wrote. “Meanwhile, the share of residents in poverty west of the river stood at 12 percent in 2015, down slightly from 13 percent in 2007.”

This suggests “continued economic depression on the east side of the river despite the economic recovery of the city as a whole” since the post-2007 recession.

From 2007 to 2015, Zippel’s report says, the share of the city’s poor residents living east of the river rose from 40 percent to 47 percent.

“The poverty rate among children living east of the river is a staggering 46 percent, compared with just 13 percent for children in the rest of the city,” she wrote. The median income citywide, adjusted for inflation, rose from $62,100 in 2007 to $75,600 in 2015, while east of the river it “remained stuck at $34,000.”

Although it is unclear whether poor black families are being pushed east of the river as a direct result of gentrification, Zippel noted that many landlords who have long provided affordable housing under contacts with the government find it hard to resist the opportunities presented by affluent newcomers.

“Owners of low-cost rent housing in gentrifying neighborhoods face significant pressure to opt out of [government] subsidies that currently keep them affordable, to hike rents, or to convert to condominiums,” she wrote.

She urged the adoption of several recommendations contained in the final report, issued this month, from the District’s Housing Preservation Strike Force, which spent more than a year studying the critical shortage of affordable housing in the city.

Among other suggestions, the study group called for the creation of a municipal office dedicated to preserving affordable housing and the establishment of a “public-private preservation fund” to aid that effort. It also recommended beefing up a city law that allows the District to purchase properties before they become unaffordable for moderate wage-earners.

“I’ve read that report and I actually attended most of their meetings,” Zippel said in an interview. “And I really think, for maintaining affordable housing, the recommendations of the strike force are exactly what the doctor ordered.”