Communities with prisons often gain political clout: Inmates are counted as local residents when it comes to divvying up government grant money and laying out legislative districts.

Big-city congressmen, whose districts typically lose in the deal, have told the Census Bureau to think about changing the arrangement — a switch that would create a mass migration of more than a million people, at least on paper.

The lawmakers want inmates counted as residents of their home towns and cities in the 2010 Census.

Many rural areas, where most prisons are located, would lose big chunks of population. Some cities would gain a lot of new "residents."

"I believe this is essentially an issue of fairness," says Rep. Jose Serrano, a Democrat from the Bronx in New York City. "Because federal dollars are distributed based on population, prisoners should be counted in their last known permanent residences where they are most likely to return to upon release."

New York City would gain about 36,000 residents if it could reclaim all its inmates in upstate prisons, according to state and federal statistics.

Many prison communities don't like the idea, arguing that they deserve benefits for housing criminals from other areas.

"We get the stigma of having these facilities," said Christopher Bromson, interim town manager of Enfield, Conn., home to three state prisons. "We get all of the ill effects of it, and now to take away the one positive. That, I think, is grossly unfair."

Bromson said his town of 45,000 would lose grant money for road construction, schools and its general budget if the 3,000 inmates were counted as living elsewhere.

The impact would be even greater in Gatesville, Texas, a city of 15,600 between Dallas and San Antonio. About half the city's population is housed in six state prisons.

Late last year Congress required the Census Bureau to study the issue. A report is due in late February.

At issue is the Census Bureau's residency rules, which, bureau officials said, would require another act of Congress to change. The bureau defines a person's "usual residence" as the place where they sleep most nights.

Jefferson Taylor, the bureau's associate director for communications, said it would be difficult to determine home addresses for many inmates, especially those on death row or serving life sentences.

"If we did this, it is very likely we would have to conduct interviews with 2 million prisoners," Taylor said. "They are not going to let us go in and conduct interviews with Charles Manson."

Gatesville City Manager Brandon Emmons said, "I think from a practical standpoint it will be a pretty tough endeavor."

Billions of dollars in federal and state grants are distributed to communities based on population. Some grants are based on per capita income, which makes prison communities eligible for more money because inmates don't have much income.

Legislative districts — local, state and federal — are drawn based on population counts in the 10-year census. America's 1,200 state and federal prisons house about 1.5 million inmates, the equivalent of about two congressional districts. An additional 500,000 are in local jails.

The Brennan Center for Justice at New York University argues that prison inmates are different from other temporary residents. The center, which advocates for inmates' rights, wants more state and federal money to go to inmates' home communities for programs to reduce recidivism.

"There is no one else who is involuntarily taken hundreds of miles from their homes to communities that they are not involved in," said Kirsten Levingston, director of the center's Criminal Justice Program. "They don't go to the libraries, they don't go to the grocery store."