PHOENIX -- There are a lot fewer people who are here illegally living in key Arizona metropolitan areas than there were a decade ago.
That's the conclusion of the Pew Research Center.
But the reasons for all that are not quite as clear.
New figures Monday show there were about 210,000 undocumented migrants in the Phoenix metro area in 2016, the most recent estimates available. That compares with about 400,000 in 2007, though there is a margin for error.
Only the New York City and Los Angeles areas had a larger drop, though both decreases were smaller on a percentage basis.
It's not just Phoenix reflecting the decline.
Tucson's unauthorized population dropped about 25 percent, from 50,000 to 35,000.
The latest estimate for Yuma is 15,000 migrants without documents, which may be a drop of about 5,000, though with the smaller numbers Pew reports the margin of error makes the accuracy less clear.
For the Prescott area, Pew reports that the 10,000 unauthorized migrants living there in 2007 may be anywhere from 25 to 50 percent less in 2016.
And in the Lake Havasu area, the Pew study said there were 5,000 people without legal status there in 2007. Now it's far fewer than that, with numbers ranging from close to zero to perhaps 3,000.
Pew researcher Jeff Passel said some of that may simply be the change in immigration patterns from elsewhere.
"We know there's been a significant drop in Mexican unauthorized immigrants over that decade,'' he said.
"And Arizona's unauthorized immigrant population is largely Mexicans,'' Passel continued. "The fact that many fewer Mexican immigrants are coming into the country and more are leaving than coming is a big factor behind this.''
Passel noted, though, there has been some research suggesting that policies adopted by Arizona lawmakers also may be a factor.
One of those is Pia Orrenius, vice president and senior economist with the Federal Reserve Bank in Dallas who looked at the requirement for employers here to use the federal E-
That requirement is part of a 2007 law, formally known as the Legal Arizona Worker Act.
It allows a state judge to suspend all business licenses of any firm found guilty of knowingly hiring those not in the country legally. A second offense within three years puts the company out of business.
Another part of that law spells out that employers must use the online system to determine whether new employees are legally entitled to work here.
There is no penalty for failing to make the checks. But those who use E-Verify have a legal defense against charges they knowingly broke the law.
The U.S. Supreme Court, in a 5-3 decision in 2011, upheld the Arizona law, rejecting arguments by the business community, Hispanic-rights organizations and the Obama administration that it infringes on the exclusive right of the federal government to regulate immigration.
"The work that we found on E-Verify found that it actually has a significant impact on the wages of likely undocumented workers,'' Orrenius said, with a specific finding of an 8 percent reduction in hourly wages.
But Orrenius said there also are larger issues at work, including an improved economy in Mexico.
And then there's the changing demographics there.
Orrenius said that the age of most migrants for economic purposes is between 18 and 24. As the number of people in that age segment decrease, she said, there are fewer to emigrate to the United States.
She had no specific studies on the effect that Arizona's SB 1070 had in reducing reduced the number of unauthorized immigrants living in the state.
That 2010 contained several provisions aimed at illegal immigration. While some were struck down by federal courts, the U.S. Supreme Court did give the go-ahead for Arizona to require that police, when they have opportunity, to ask the immigration status of those that they stop.
The Pew study also finds mixed results across the country.
Overall, the report says the unauthorized population in the United States dropped from about 12.2 million in 2007 to 10.7 million in 2016. And while most of the metro areas showed a decline or no significant change, there were a few areas with increases.
Most notable is the Washington, D.C. area where the number of
people not in this country legally is estimated to have increased by 100,000 between 2007 and 2016, to 425,000.