MEXICO CITY — A new report by U.S. and Mexican researchers suggests an uptick in the number of illegal migrants headed to the United States in the first half of 2012, and a slight decrease in migrants returning to Mexico.

The report by Mexico's Colegio de la Frontera Norte and the University of Southern California's Tomas Rivera Policy Institute says the U.S. Mexican migrant population appears to have stabilized and may be growing slightly.

It would be the first time net migration outflow from Mexico has increased since the 2007 economic downturn.

The report released Tuesday says that heightened U.S. anti-immigration efforts don't appear to have convinced migrants to leave.

The report is based on surveys done at Mexican border crossings, bus stations and airports, and on U.S. deportation, repatriation, and demographics data.