A new study has found that there is an 11 percent drop in the number of illegal immigrants in the United States due to the enforcement mesaures taken by the Bush administration.

From the LA Times:

The report by the Center for Immigration Studies, a Washington-based think tank, says that the number of illegal immigrants fell about 11% between last August and May, from 12.5 million to 11.2 million.

The study was based on an analysis of census data and concludes that if that rate of decline is sustained, the number of illegal immigrants will be halved in five years.

Steve A. Camarota, the center’s research director, acknowledged that the economy played a role in the decline but said that several factors pointed to enforcement as key. For instance, the legal immigrant population continues to grow, while the fall-off in illegal immigrants began even before unemployment began rising.

“It seems that increased enforcement has played a significant role,” Camarota said.

Camarota also said the data suggested that many illegal immigrants were leaving of their own accord. The decline in their number is much larger than the tally of those removed by the government, the report says.

The Pew Hispanic Center, according to the article, does not agree with the figures.

Independent demographers said they also had seen a drop in the illegal immigrant population. But some questioned the study’s methodology, decline figures and underlying assumptions.

“Our data aren’t inconsistent with the idea that people are leaving,” said Jeffrey S. Passel, a senior demographer with the Pew Hispanic Center, a nonpartisan Washington think tank.

But he added: “I don’t see in my numbers anywhere near the decline he’s talking about.”

Human smuggling is a $10 billion market.