A new study by the immigration issues group Center for Immigration Studies suggests an amnesty for illegal immigrants would cost taxpayers $19 billion.

The think tank, which supports reducing immigration and has testified in Congress against guest worker legislation, based its study on 2002 information on the fiscal costs and benefits of the nation's estimated 8 million illegal immigrants.

The study, by Steven A. Camarota, the center's director of research, said legalized immigrants would be much more likely to file federal income tax returns, but would also be able to tap into social programs such as Social Security, Medicare, welfare and federal education aid.

Camarota said households headed by illegal immigrants cost the federal government $10.4 billion in 2002, and if they were legalized, that net cost would grow to nearly $29 billion.

Pam Perlich, senior research economist at the University of Utah's Bureau of Economic and Business Research, the study only looks at one point in time.

"It's pretty narrow, just focusing on households, rather than the broader view of overall immigration," she said. "I would prefer a more dynamic approach."

Perlich said about one in three of Utah's immigrants are here illegally, often taking low-skilled jobs that native workers don't want.

Perlich said the study did not consider labor market effects, or immigrants' contribution to the nation's economic growth. It also failed to look at the impending crisis for the Social Security system as the nation's work force ages, and fewer young workers are left to fill in the gap, she said.

"That's why people are coming, because of the jobs," she said. "At the low end of the wage scale, we'd have labor shortages if they were not here, and increases in the price of agricultural products."

Camarota said it's the social benefits provided to the working poor that would increase the fiscal cost if illegal immigrants were given amnesty.

"It's employed people who cost all the money," he said. "Welfare mainly goes to people who work."

Camarota pointed to the earned income tax credit, which requires a federal tax return be filed.

"Right now illegal aliens only account for 1.5 percent of the cost of the EITC," he said. Legalizing immigrants would increase that cost "tenfold."

Camarota acknowledged that if those immigrants were legalized, "their tax payments would go up 77 percent on average," but the average cost to government would rise by 118 percent.

"Illegal immigrants pay $16 billion in taxes to the federal government," Camarota said. "That's hardly a trivial sum."