Fewer Mexicans are entering the U.S. -- down by about half, from 3 million to 1.4 million -- and more are returning to their homeland -- nearly doubling in the five-year period of 2005-2010 to almost 1.4 million, from 667,000 the previous five years, the study reported.
Groups working in the municipalities abandoned by Mexican migrants found validity in the study, but called for a nuanced reading of the data and cautioned against concluding that outward migration had collapsed or that the trend would not be reversed.
"Without doubt, immigration has gone down a little, but that doesn't mean it's now collapsed," said Scalabrini Sister Leticia Gutierrez, director of the Mexican bishops' human mobility ministry.
"The numbers (in the report) are in line with what we're seeing here," said Ellen Calmus, who directs The Corner Project, which works with migrant families in Malinalco, southwest of Mexico City.
"Zero or less total immigration is actually an averaged-out number: It doesn't mean that people are not going north, only that the total new arrivals are equal or less than the total who are leaving," she added.
Outward migration has marked Mexico for generations as young men would come and go, crossing the border with ease to take temporary jobs -- often in agriculture and construction. The migration exploded during the 1990s and early 2000s, and Mexicans abroad began sending home increasing amounts of money -- more than $20 billion, according to the Bank of Mexico. The money propped up villages left behind and maintained families.
The numbers then started declining, for numerous reasons.
The Pew report and immigration observers cited factors for the decline such as the U.S. economic downturn in 2008 and decimation of the construction industry that employed so many Mexican migrants.
Other factors cited include an increased fortification along the U.S.-Mexico border, increased immigration enforcement and a surge in laws deemed unfriendly to undocumented migrants.
Calmus said migrants from her area now stay longer in the United States, instead of working for a year or two, then rejoining their loved ones. The change is "causing tremendous difficulties to families here, who never expected their migrant relatives to be gone for so long," she said.
The Mexicans returning south express less of a desire to return than those deported during past years. The Pew report found: 60 percent of those surveyed in 2010 wanted to head back north, a drop from 83 percent in 2005. The composition of those being returned also changed with many Mexicans arriving with U.S.-born children.
"We are definitely seeing evidence of an increasing number of returnee families in the growing numbers of U.S.-born children in the schools," Calmus said.
The report cited improvements in Mexico over the past decade and demographic changes -- fertility rates have dropped -- as other possible reasons for diminished migration.
"The fact is that it's due to various factors because we're creating employment opportunities in Mexico, training and educational opportunities for young people and health services," President Felipe Calderon said of the Pew findings April 24 in Washington.
Per capita gross domestic product has grown 22 percent in Mexico since 1980, Pew said, compared with 66 percent growth north of the border. But Mexico has had macroeconomic stability in recent years marked by low interest rates, low inflation and an expansion of credit.
Millions of families have purchased new homes with mortgages since 2000 through a program of worker, employer and government contributions known as Infonavit. The number of new cars has increased by 8 percent annually over the past 20 years in Mexico City, and the country is on pace to achieve universal health coverage.
"You have a slight improvement in Mexico's economic indicators," said Manuel Molano Ruiz, adjunct director of the Mexican Institute for Competitiveness.
But he cautioned against crediting any one thing for the decline in migration, saying, "It's difficult to separate out the causes."