While the size of the illegal immigrant workforce in this country has changed little since the worst of the recession, a substantial number of these unauthorized workers have moved into better-paying white-collar jobs, according to a new study by the Pew Research Center.

For sure, a solid majority of the 8.3 million illegal immigrants continue to work in low-skilled service, construction and production jobs. Yet the number of unauthorized immigrants in management or professional related jobs grew by 180,000 since the 2007-2009 Great Recession, while the number in construction or production jobs fell by about 475,000.

Related: Obama's Immigration Order Blocked by Federal Judge

The findings are “a reflection of changes in the overall economy” since the recession, according to demographics experts Jeffrey S. Passel and D’Vera Cohn, essentially mirroring rises and declines in the overall U.S. economy.

The share of all unauthorized immigrant workers with management and professional jobs grew to 13 percent in 2012 from 10 percent in 2007, according to the study, while the share with construction or production jobs declined to 29 percent from 34 percent.

“Certainly the economy has moved more in that direction. Overall the white collar workforce has grown and the blue-collar work force has declined in the last few years, so in that sense the unauthorized immigrant workforce is just reflecting the larger economic trend,” Cohn said in an interview today. “What we don’t know is whether the people who” previously were in blue collar jobs are the ones holding those jobs now.

“It seems implausible that people who were construction laborers five years ago are now software developers,” she added. “In many cases these are different people, although some people may have moved up the ladder.”

Passel noted that many illegal immigrants have now lived and worked in the U.S for ten years or more and have been able to land better jobs in their occupational fields, such as managers, while others have obtained work permits under the president’s executive action or decided to overstay their visas. “Remember, now there are about 600,000 people who have gotten work permits under the Dream Act, and those are all people who went to college pretty much,” he said.

Even with these shifts, illegal immigrant workers remain concentrated in lower-skill jobs, much more so than American-born workers, according to the new estimates, which are based on government data. According to the study, 62 percent held service construction and production jobs in 2012, twice the share of U.S.-born workers who did.

The 13 percent share with management or professional jobs is less than half of the 36 percent of U.S.-born workers in those occupations, Pew said.

Related: Immigration Fight with Obama Risks Republican Unity

These new findings come at a time when the new Republican controlled Congress and President Obama are deadlocked over immigration policy – particularly the president’s highly controversial executive orders to protect most illegal immigrants from deportation and to grant many of them legal status to enable them to more readily find and keep jobs.

Republicans threatened to partially shut down the Department of Homeland Security in a move to block implementation of the executive orders, but backed down at the last minute. Still, Obama’s new policies have been held in abeyance pending a federal court challenge in Texas.

Many conservatives are enraged that Obama would take actions to essentially assist illegal immigrants or foreign workers with temporary visas to compete with unemployed Americans for jobs during the middling economic recovery.

Sen. Jeff Sessions (R-AL), a leading conservative opponent of Obama’s amnesty policies, has charged that the president’s immigration policies are hurting average American workers.

Sessions has noted that since the 2007 recession, most employment gains in the U.S. have gone to imported workers instead of American citizens. “On immigration, the president remains wedded to a lawless policy that serves only the interest of an international elite while reducing jobs and benefits for everyday Americans,” he told Breitbart.com in January.

Top Reads From The Fiscal Times