Allowing illegal immigrants to pay in-state tuition rates at Maryland colleges and universities would cost state and local taxpayers several million dollars each for each class that goes through the system, according to a new report.

The federal government would also have to pay about $50,000 a year for each class, adding up to state, local and federal governments sharing a total cost of nearly $7.5 million a year starting in 2016, if voters approve the Maryland Dream Act on the November ballot.

The study by the Maryland Institute for Policy Analysis and Research at the University of Maryland Baltimore County found that eventually these costs would be offset by increases in income and sales taxes, as well as decreases in the costs of operating prisons, "because more educated individuals are less likely to commit crimes and be incarcerated."

But opponents of the Dream Act warn that even if the benefits outlined in the report are realized, they will be dwarfed by costs to taxpayers from more illegal immigrants coming to the state to take advantage of the law.

Del. Neil Parrott, R-Washington County, who led the fight to get the law on the November ballot, said the state spent $1.6 billion providing services for illegal immigrants in the past year, including housing, health care, school and other costs.

The authors of the report, however, do not believe that passing the Dream Act is likely to increase the number of illegal immigrants coming to Maryland.

The study estimates that over the lifetime of members of each class helped by the law there would be a benefit of $24.6 million for the class, most of that from federal and state taxes paid on increased incomes.

"It is indeed a long-term investment," said UMBC public policy professor Marvin Mandell, one of the study's authors. "The short run and long run is a lot like any other investment that governments make, and if there's a short-run cash shortage, governments can borrow -- and do all the time -- against future benefits."

The idea that the law would benefit the state financially is based on a number of assumptions; that the students would find jobs when they graduated, that their incomes would increase gradually over time and that the majority of graduates would stay in the state.

And if all these assumptions are true, "the benefits would occur relatively slowly -- when the first [class] graduates college, [the benefits] ramp up for four years, and then they continue to ramp up because people earn more in their 30s than in their 20s," Mandell said.