As a lot of work is undertaken by men from Mexico and Central America, most of them in this country illegally, undocumented immigrants "are a pillar of California's economic strength." the paper claimed.

Immigrants, economists contend, contribute to consumer spending and, instead of replacing native workers, create jobs, the paper said.

"The American engines of industry and commerce have always been fueled by a steady supply of new arrivals," it said.

"Overall, immigration has been a net gain for American citizens, though a modest one in proportion to the size of our 13 trillion-dollar economy," 500 economists wrote in an open letter to Congress on June 19.

The economists concede that a "small percentage" of native-born Americans may be hurt by competition from illegal immigrants who are willing to work cheaply. But any harm, they say, is outweighed by the benefits to the overall economy.

Although measuring the contributions of illegal workers is a difficult task, special interests that benefit from immigrant labor - including agribusiness, restaurant operators and unions courting new members - tout their gains as gains for all, said Michael Teitelbaum, who was vice chairman of the bipartisan U.S. Commission on Immigration Reform in the 1990s.

For example, restaurant prices are pushed down by illegal labor in the kitchen, fruit and vegetable prices by illegal field hands, new-home prices by illegal drywallers, said the paper.

Immigrants are not just a weapon against inflation. The tens of thousands of illegal nannies in the Los Angeles area, for example, lower the cost of child care, freeing mothers to return to work. This in turn increases families' incomes, which encourages spending and fuels the economy, according to the paper.

Many immigrants send a portion of their earnings home to their families, but their influence here remains potent. The Economic Roundtable, a Los Angeles think tank, estimates that the 400,000 illegal workers in L.A. County spend 5.7 billion dollars annually on food, rent, transportation and other necessities.

The presence in the United States of 12 million illegal immigrants is one of the most contentious issues of the era in the United States. Hundreds of thousands of immigrants have repeatedly demonstrated this year for legal recognition, sparking a backlash from many native-born Americans. Congress has been stalemated between legalization advocates and those pushing punitive measures.