When senators tried to pass a “comprehensive immigration bill” last June that would have established a guest worker program for illegal immigrants, many conservatives decried the legislation as amnesty and demanded that the border be secured first.

According to a new study, their outrage may have paid off.

A compilation of data by the Center for Immigration Studies released Wednesday found that since the immigration bill failed to pass the Senate last June, the number of estimated illegal immigrants in the country has declined from about 12.5 million to about 11.2 million, an 11 percent reduction.

This decline began in August 2007, less than two months after the legislation was voted down, and followed a sudden spike in the number of illegal immigrants in the country, which had started in March 2007.

The study measured only Hispanic immigrants ages 18-40 with a high school degree or less of education. Two-thirds of illegal immigrants fit this profile, according to the CIS.

Meanwhile, the population of legal immigrants experienced no decline and has actually grown steadily since June 2007.

“This is the first actual data that demonstrates that something is, in fact, happening here,” said Mark Krikorian, executive director at the CIS.

The study found that the change resulted primarily from illegal immigrants leaving the country to return to Mexico.

Steve Camarada, the director of research at CIS, said that the two most likely factors responsible for this out-migration were increased border enforcement and the lagging economy. But immigrant unemployment rates remained steady until December 2007, long after the exodus of illegal immigrants had begun.

In the past, waves of immigrants leaving the country had always followed spikes in immigrant unemployment, according to Camarada. Continued...