A study on immigrants’ integration conducted by a Duke University economist and sponsored by the Manhattan Institute, a free-market-oriented conservative think tank in New York City, informed that modern-day immigrants assimilate more quickly than previous generations.

The study was based on U.S. Census Bureau and other survey data to create an assimilation index for measuring the degree of similarity between the U.S.’ foreign-born and native-born population. The economic, cultural and civic areas were taken into consideration: earnings and rates of homeownership, English ability and degree of intermarriage with U.S. citizens, rates of U.S. citizenship and service in the military. The higher the number on a 100-point index, the more an immigrant resembled a U.S. citizen.

The study’s result was a positive one, with some exceptions.

According to the study, Mexicans, the largest immigrant group, are making slower progress than others.

The report also found that the speed with which newcomers take on native-born traits has increased since the 1990s.

“The bottom line is there are some encouraging things and some things to be concerned about, but the nation’s capacity to integrate new immigrants is strong,'” said the study's author, Jacob L. Vigdor, as the Washington Post reported.

Vigdor explained this as a consequence of the economic expansion of the 1990s which created more job opportunities.

Surprisingly, “one of the top five origin countries was England, and close to 100 percent of them spoke English,” Vigdor said. There are also big differences between immigrants from certain countries. Mexicans, for example have an index of 13, while Vietnamese were at 41. A major reason for these disparities in assimilation levels may be the high percentage of Mexican immigrants who are in the country illegally, Vigdor said.

“If you’re in the country illegally, a lot of the avenues of assimilation are cut off to you. There are lots of jobs you can't get, and you can't become a citizen,” he said.

According to the Miami Herald, the study - “Measuring Assimilation in the United States”- is meant only to inform, not to make recommendations, Vigdor said in a phone conference Monday.