(CNN) -- The number of Mexican migrants returning to their country -- mainly from the United States -- has increased dramatically in the last five years compared with the previous five years.
According to the most recent numbers released by the Mexican census bureau, the increase was 31.9% in the period from 2005 to 2010, compared with 2000 to 2005 numbers.
The Mexican Institute of Statistics and Geography -- INEGI by its Spanish acronym -- says that during the last five years of the decade, 1.1 million Mexicans left their country. According to the government agency, by the time the national census was taken last summer, more than 351,000 Mexican migrants had returned to Mexico.
Two factors played a role in changing the pattern, according to Eduardo Sojo, INEGI's president,
"The first factor was the situation of the economy in the United States, which decreased the number of (employment) options for migrants. The second factor was the increasing difficulties migrants have when they attempt to cross the border (illegally)," said Sojo.
The economic downturn that hit the United States towards the end of 2008 had a negative effect on American manufacturing firms that traditionally employed Mexican migrants, legal or otherwise. Many Mexican laborers with no specialized training had no option but to return home.
Many of those returning to Mexico had migrated to the United States in the early and mid-1990s when the trek north was easier and safer. There was also a higher demand for unskilled labor in the manufacturing and construction sectors, which declined dramatically in 2008.
Crossing the border from Mexico also became more difficult, making the life of a migrant increasing difficult and dangerous. In the last decade, the U.S. Border Patrol more than doubled the number of its agents positioned along the critical 262 miles of what is known as the Tucson Sector (most of the Arizona border) to 3,400 agents. The area had become a busy crossing point in previous years, as U.S. efforts to tighten the border in other areas pushed migrants toward Arizona.
In 2000, the number of arrests made by border patrol agents in the Tucson Sector was 616,000. By 2005 the number had decreased to 439,000. Last year it was 212,000, reflecting both the increased law enforcement presence on the U.S. side and the decreased numbers of migrants attempting to cross from the Mexican side.
U.S. Border Patrol Agent David Jimarez says the change has to do with increased resources and personnel in this sector. "If you go ahead and take a look at a couple of things that have taken place here in the Tucson Sector you'll notice that there's been an unprecedented amount of technology, infrastructure, as well as personnel being deployed towards the border. That's the amount of dedication that's being given to border enforcement right now," says Jimarez.
Thus crossing the border illegally became significantly more difficult, costly, and dangerous for Mexican migrants, involving ruthless and abusive smugglers charging thousands of dollars for a trip by foot through the middle of the unforgiving Arizona desert where hundreds die each year trying to reach the American dream.
Not only have migratory patterns from Mexico to other countries been reversed in recent years, but patterns within Mexico itself have shown a dramatic reaction to drug cartel violence in Mexican border towns.
Statistics released by INEGI also show that Mexicans are fleeing in droves from border cities that have seen a sharp increase in violence. The 2010 census says that as much as 18.5% of homes in some border cities are abandoned. In Ciudad Juarez -- the most violent city in Mexico, located in the state of Chihuahua, just south of El Paso, Texas -- the number of abandoned houses is 31 percent higher than the national average, according to INEGI.
Last November, about 100 families in the border town of Ciudad Mier -- near Laredo and McAllen, Texas -- abandoned their homes almost overnight.
What prompted people to flee in panic was a rumor that the Gulf cartel was about to carry out a massacre in retaliation for the killing of Ezequiel Cardenas-Guillen. The alleged cartel leader had been gunned down in early November by Mexican security forces.
Ciudad Mier, with a previous population of 6,500, became something of a ghost town and has yet to recover.