HARLINGEN, Texas — Salvador Munoz spends long days working in the heat of southern Texas aloe vera fields. Then he works a few odd jobs at night.

But the 62-year-old Mexican immigrant doesn't spend much of the roughly $200 he earns each week. Instead, he sleeps at a homeless shelter and gets by on three tacos a day and a visit to the soup kitchen — all so he can send money home for his 13 children.

Munoz is one of an estimated 10 million migrants contributing to what a recent survey says is a $30 billion-a-year infusion into the Latin American economy.

"The money from here helps for there," said Munoz, who is from the central Mexican state of Queretaro. "That's why the Mexican government likes for us to come over here, why they try to get us permits. We save and send back money and the people there can do something."

The $30 billion estimate by the Inter-American Development Bank's Multilateral Investment Fund, which promotes Latin American investment, is up from $23 billion in 2003.

The investment fund released its estimates this month based on Census data and a survey of about 4,000 Latin Americans — 32 percent of them illegal immigrants — from Mexico, Central America, South America and some Caribbean nations.

The $30 billion figure surpasses all aid to Latin America by developed nations, said Inter-American Development Bank manager Donald F. Terry. That would make remittances, as the money sent home is called, the third-biggest economy in Latin America, he said.

Some economists and migrants say the money feeds a growing Latin American middle class and pays for schools, land and small businesses. Critics say much of the money goes toward bringing new illegal immigrants into the country.

Regardless, Munoz and others say the long hours working in the United States are worth it.

The money Munoz sends home pays for a 15-room concrete house in Mexico, a farm, a small store and his children's school fees, he said. Munoz, who immigrated at age 16 after his parents died, used to stay in the United States for years at a time. Now, he can afford to go home every summer.

Constantino Gonzalez Padron, 43, has traveled back and forth to New Jersey to work for 16 years. He earns up to $135 a day erecting fences and digging holes for swimming pools, and sends nearly all his money back to support his wife and three children in Mexico.

"I send most of it, except what I need for my basic needs — insurance, food, my fourth of the apartment," said Padron, who lives with three other Mexican migrants.

Terry called the remittances key to "financial democracy" in Latin America, but immigration

watchdog groups say they are worried by the data.

"It is highly questionable whether the $30 billion sent back to Mexico and Latin America offsets the loss of their most productive workers and the lost opportunities for economic and political reform that might have occurred in those countries if the United States did not provide a constant safety valve for millions of dissatisfied workers," said Dan Stein, executive director of the Federation for Immigration Reform.

"Having an entire region dependent on sending their workers out of the country and waiting for them to send home a few dollars every month is bad economic and social policy," he said.

Stein questioned how much of the money was used to help more migrants enter the United States and what the burden was on the U.S. taxpayer.

But Pia Orrennius, an economist at the Dallas Federal Reserve, said the data indicated one of the biggest fears about the migrant workforce was wrong — that immigrants are taking jobs in urban areas away from U.S. citizens.

"You can see a lot of recent immigrants have relocated in nontraditional states like North Carolina and Georgia," she said. "In the 1990s we didn't have this very interesting dispersal of Hispanic immigrants into new areas."

While the data shows the most remittances come from California ($9.6 billion), New York ($3.6 billion) and Texas ($3.2 billion), other states are catching up.

"We have these very large regional impacts where local labor markets would not be able to grow without immigrant labor — states in the West and Midwest like Minnesota and the Dakotas are areas where natives are leaving, and the only people coming in to sustain this economic growth are immigrants," Orrennius said.