By the CNN Wire Staff

(CNN) - Net Mexican immigration to the United States has slowed to a standstill, according to a report released Monday.

The number of immigrants coming from Mexico to the United States has steeply declined while the number of Mexicans leaving the United States has increased sharply, the Pew Hispanic Center said.

"These developments represent a notable reversal of the historic pattern of Mexican immigration to the U.S., which has risen dramatically over the past four decades," the center's report says.

Many factors are probably behind the trend, the report said, including rising deportations, greater enforcement at the border, growing dangers associated with border crossings, the weakened U.S. job market and a long-term decline in Mexico's birth rates.

The 1.37 million Mexican immigrants who came to the United States between 2005 and 2010 was about half the number who immigrated during previous five-year periods, according to the analysis, which was based on national population surveys in the United States and Mexico.

Meanwhile, from 2005 to 2010, 1.39 million Mexicans and their families left the U.S. to return to Mexico, the report says. That's more than double the number of people who did it during a five-year period the decade before, the report says.

The report also notes, citing figures from the U.S. Department of Homeland Security, that the number of Mexicans apprehended trying to cross the border illegally has plummeted in recent years, from more than 1 million in 2005 to 286,000 in 2011.

While analysts said for years that immigration from Mexico to the United States was dwindling, the Pew report says 2010 Mexican census data offer some of the first "hard evidence that flows back to Mexico had grown over the same period."