The Mexican government reported the results of recent studies on Tuesday showing that 68 percent of Mexicans who migrate or try to migrate to the United States do so without documents and 55 percent of them hire immigrant smugglers.

The report, timed to coincide with the U.N. International Migrants Day, also noted that the Mexican-born population living in the United States increased from about 800,000 in 1970 to more than 11 million in 2006.

The majority of Mexicans now living in the United States — 6.2 million — are undocumented, according to the report, which was based on surveys of migrants and information from the government's National Population Council.

Almost 30 million people in the United are direct descendants of Mexico migrants, the report stated.

In contrast, the report said the immigrant population in Mexico is quite small and has not experienced rapid growth.

The number of foreign residents in Mexico grew from 340,000 people en 1990, or about 0.42 percent of the population at the time, to about 493,000 in 2000, or about 0.5 percent, the last year for which data is available.

More than two-thirds of the foreign residents are from the United States, and many of those are of Mexican extraction.