On Utah's homefront, evidence from the Social Security Administration and the Utah State Tax Commission points to tax contributions by at least some illegal immigrants.

There were 17,165 people who filed 2003 Utah state tax returns using ITINs, or tax identification numbers for those who don't qualify for Social Security numbers. Those filings totaled $3.5 million.

Overall, Utahns paid $1.6 billion in 2003 state income taxes.

But it is much more difficult to quantify the revenue impact of illegal immigrants to the Utah economy, says Robert Spendlove, an economist from the Utah Governor's Office of Planning and Budget.

No surprise, Perlich says.

No employer is going to admit how hard illegal immigrants work. No undocumented worker is going to come out and say they'll work for less under worse conditions.

"What you have is essentially a bunch of people who fly below the radar, and a bunch of employers who benefit financially every day," Perlich said. "Nobody's got the incentive to identify them."

If the government was really serious about not wanting to have illegal immigrants working here, it would crack down on employers, Perlich says. "If employers were forced to be responsible for this, it would not be an issue, because the people are coming for jobs."

The Immigration Reform and Control Act of 1986 requires employers to examine documents that establish an employee's identity and eligibility to work in the United States. The act requires an "I-9" employment verification form that must be kept on file.

One of the challenges of enforcing the employment law has been a proliferation of counterfeit documents, saysVirginia Kice, spokeswoman for U.S. Immigration and Customs Enforcement.

"We have to be able to prove the employer knowingly hired someone who is not authorized to work," Kice said.

An employer can call the Social Security Administration or ICE to find out if a Social Security number is valid. The Salt Lake ICE office reports no such calls.

Many employers don't take the optional step of verifying an employee's information through a federal agency. Some say the system isn't user friendly, or that they don't need to use the system because they don't hire anyone who is questionable. A few say they weren't aware that they could verify the information with a federal agency.

While verification is currently optional, a recent Deseret Morning News/KSL-TV poll found that 93 percent of respondents believed it should be made mandatory.

By most accounts, few employers are taking extra steps to verify Social Security numbers and documentation.

Ask the houseful of undocumented workers in Heber who all work at construction or restaurant jobs in Park City.