The report said there are 110,000 undocumented immigrants in Utah down 10,000 from 2007 but well above the 2000 level of 65,000.
When taken together, Utah, Arizona and Nevada grouped as the Intermountain West saw the total number drop from 850,000 in 2007 to 700,000 in 2010.
Researchers at Pew were unable to say exactly why the decrease occurred, though they did suggest economic and enforcement factors likely played a role in the new data.
Jeffrey Passell, senior demographer with the Pew Hispanic Center, said Utah's decline wasn't due to being influenced by Nevada and Arizona's flagging housing market and, in turn, struggling economies.
"Whether Utah is different from Arizona or Nevada, we really can't say, but they did show individually a decline on their own," Passell said.
But he hesitated to say there was an impact based on the passage of enforcement-heavy laws or bills that target undocumented immigrants by allowing local police to act as federal immigration officers in using "reasonable suspicion" standards.
The Utah numbers weren't surprising to Pam Perlich, senior economist at the Bureau of Economic and Business Research at the University of Utah.
"Much of the sustained net in-migration to Utah in the 1990s and beyond was tied to the construction boom and housing bubble," Perlich said. "Both, of course, came to an abrupt end and, as a result, job losses in construction have been very severe. This is the sector employing many immigrants, including the undocumented."
In Utah, the number of undocumented workers topped out at 75,000 about 5.4 percent of the total work force.
The national numbers on illegal immigration also reflected a slight decline from 2007 but were relatively unchanged from 2009, when the number of undocumented immigrants stood at 11.1 million.
According to the report, the total number of undocumented immigrants declined from 12 million to 11.1 million in that three-year span. And the number of them in the work force dropped from 8.4 million in 2007 to 8 million again in that three-year stretch.
Most of the undocumented people came from Mexico a total of 70 percent. The remaining 30 percent came from Latin America, Canada, Europe and Asia.
Perlich didn't think the new numbers would change the focus of the debate on immigration reform, as the Utah Legislature begins tackling the thorny issue.
"I do not imagine the release of these estimates will dissuade legislative efforts to pass enforcement-only bills," she said.
Rep. Stephen Sandstrom, R-Orem, said the new numbers weren't surprising to him, either.
But Sandstrom saw the new data as a better opportunity to pursue his bill, HB70, that requires local police to enforce federal immigration law through "reasonable suspicion," when a suspect is caught committing a crime or a traffic infraction.
Sandstrom said the lull in migration is "the perfect time" to pass tough enforcement-only immigration laws.
"We have a problem, and if the numbers are down, it means maybe there won't be as much impact," Sandstrom said.
"But once the economy starts rolling again which we know it will I think you'll see the numbers shoot back up, unless we have an enforcement bill in place."
Michael Clara, chairman of the Utah Republican Hispanic Assembly, said the report pokes a big hole in claims made by Sandstrom and Rep. Chris Herrod, R-Provo, that undocumented immigrants are leaving Arizona and coming to Utah.
"The latest report confirms what we are seeing in our communities the undocumented population in Utah is shrinking in response to the economy," Clara said. "Representatives Sandstrom and Herrod would have us believe that all the undocumented residents in Arizona are making their way to Utah, and this simply isn't true."
Currently, there are four main immigration bills vying for attention in the Legislature, including a employer-penalty program authored by Herrod and a repeal of in-state college tuition for undocumented students sponsored by Rep. Carl Wimmer, R-Herriman.
Another bill authored by Sen. Luz Robles, D-Salt Lake City, has an enforcement component but also establishes an identification system for those already living in the state for two or more years.
There may be as many as 20 immigration-related bills that lawmakers will deal with before the session ends March 10.
Change over time
Estimated number of immigrants in Utah illegally during past 20 years:
1990 • 15,000
2000 • 65,000
2005 • 95,000
2007 • 120,000 (peak)
2010 • 110,000
Source • Pew Hispanic Center
The Pew Hispanic Center report highlighted the following
The number of unauthorized immigrants decreased from 2007 to 2010 in Colorado, Florida, New York and Virginia. The combined population in Arizona, Nevada and Utah also declined.
In contrast to the national trend, the combined unauthorized immigrant population in Louisiana, Oklahoma and Texas grew from 2007 to 2010.
Although the number of unauthorized immigrants in the U.S. is below 2007 levels, it has tripled since 1990, when it was 3.5 million, and grown by a third since 2000, when it was 8.4 million.
Source • Pew Hispanic Center