WASHINGTON – The number of immigrants crossing the border illegally into the United States appears to be on the rise again after dropping during the recession.

The total number of immigrants living in this country unlawfully edged up from 11.3 million in 2009 to 11.7 million last year, with those from countries other than Mexico at an apparent all-time high, according to a report released Monday by the Pew Research Center's Hispanic Trends Project.

The change is within the margin of error, and there will be a more precise census measure released later this year. Still, based in part on other factors such as increased U.S. border apprehensions, the sharp decline in illegal immigration from 2007-2009 has clearly bottomed out, with signs the numbers are now rising, Pew said.

Pew said that among the six states with the largest numbers of immigrants here illegally, only Texas had a consistent increase in illegal immigration from 2007 to 2011, due in part to its stronger economy. Its number was unchanged from 2011 to 2012. Two states — Florida and New Jersey — had an initial drop but then increases during the same 2007-2011 period. Three states — ­California, ­Illinois and New York — showed only declines.

"As a whole, with the recession ending, the decrease in illegal immigration has stopped," said Jeffrey Passel, a senior demographer at Pew.

Construction jobs attract

Passel noted that historically the level of illegal immigration has been closely tied to the strength of the U.S. economy and availability of jobs. Since 2009, the average U.S. jobless rate has dropped from 9.3 percent to 8.1 percent last year, with signs of strength in the construction industry, which yields jobs generally attractive to newly arrived Latino ­immigrants.

, Star Tribune
In this June 13, 2013 file photo, Daniel Zambrano, of Tijuana, Mexico, holds one of the bars that make up the border wall separating the U.S. and Mexico where the border meets the Pacific Ocean in San Diego.

The Pew analysis is based on census data through March 2012. Because the Census Bureau does not ask people about their immigration status, the estimate on illegal immigrants is derived largely by subtracting the estimated legal immigrant population from the total foreign-born population. It is a method that has been used by the government and Pew for many years and is generally accepted.

Analysts said it is hard to predict whether immigrants in the country illegally could eventually exceed the record total of 12.2 million in 2007. Continued modest increases are possible, but another big surge like the one seen in the late 1990s and early 2000s isn't likely, due in part to demographic factors such as ­Mexico's aging workforce.

"Labor demand in the U.S. is still slack and wages are eroding, whereas there are jobs in Mexico and wages are slowly rising as labor force growth there decelerates," said Douglas Massey, a professor of sociology and public affairs at Princeton University who is co-director of the Mexican Migration Project. "The pressures for mass migration are diminishing for now, but who knows what kind of disasters lie ahead?"