MEXICO CITY – The amount of money Mexicans sent home suffered its sharpest drop on record in July as the U.S. economy slowed and the dollar fell, Mexico's central bank reported Monday.

Remittances – Mexico's second-largest legal source of foreign income after oil – dropped by 6.9 percent in July compared to the year before.

“This is the sharpest drop we have seen,” said Jesus Cervantes, director of economic measurement for Mexico's central bank. The worst previous year-over-year monthly decline was 6.3 percent in January.

Cervantes said that over 20 percent of Mexican migrants work in construction in the United States, a sector hit particularly hard by the U.S. mortgage crisis. “Basically, the job situation for Mexican migrants in the United States has become complicated,” he said.

Records dating back to 1995 on the central bank's Web site showed no greater monthly fall, and records kept before then are considered unreliable.

Mexicans who depend on money sent home are also suffering from an 8 percent drop in the value of the U.S. dollar against the Mexican peso this year.

The bank said remittances for the first seven months of the year are 2.9 percent below what they were in 2007.