Over at Hit and Run David Weigel blogs on a Washington Post report on a new study from the Manhattan Institute that he describes as “revealing the quicker and quicker adaptation of immigrants to American norms.” He pulls the following excerpt:

In general, the longer an immigrant lives in the United States, the more characteristics of native citizens he or she tends to take on, said Jacob L. Vigdor, a professor at Duke University and author of the study. During periods of intense immigration, such as from 1870 to 1920, or during the immigration wave that began in the 1970s, new arrivals tend to drag down the average assimilation index of the foreign-born population as a whole.

The report found, however, that the speed with which new arrivals take on native-born traits has increased since the 1990s. As a result, even though the foreign population doubled during that period, the newcomers did not drive down the overall assimilation index of the foreign-born population. Instead, it held relatively steady from 1990 to 2006.

“This is something unprecedented in U.S. history,” Vigdor said. “It shows that the nation’s capacity to assimilate new immigrants is strong.”

Unfortunately, Weigel only mentions a small portion of the findings of the report. The second paragraph of the Post article cited by Weigel paints a very different picture of the immigration landscape:

Modern-day immigrants arrive with substantially lower levels of English ability and earning power than those who entered during the last great immigration wave at the turn of the 20th century. The gap between today’s foreign-born and native populations remains far wider than it was in the early 1900s and is particularly large in the case of Mexican immigrants, the report said.

Vigdor goes on to explain why, given this information, the assimilation index has gone up (emphasis mine):

A possible explanation, Vigdor said, was that the economic expansion of the 1990s created more job opportunities at all levels, speeding the economic integration of immigrants. It could also be that because today’s immigrants begin at such a low starting point, “it’s easier to make progress to the next level up” of integration than it would be if the immigrant had to improve on an already high level of integration.

A report from The New York Sun analyzes the findings and ascertains that, while the overall immigration index is satisfactory for Weigel, the overall rating is still lower than during the 20th century immigration wave, and that the Post report masks some disturbing trends in assimilation among the Central American and Mexican populations.

The current overall assimilation level for all immigrant groups combined, measured on a scale of zero to 100, is, at 28, lower now than it was during the great immigration wave of the early 20th century, when it never went below 32. What’s more, the immigrant group that is by far the largest is also the least assimilated. On the zero-to-100 scale, Mexicans — 11 million emigrated to America between 1980 and 2006 — score only 13.

Although Mexican assimilation does occur, it’s extremely slow. Mexicans who arrived in 1995 started out with Index scores around five — and increased only to around 10 by 2005. In other words, our largest immigrant group arrived with little education and even less knowledge of English, and they have stayed that way for an extended period.

It is also noteworthy that the Manhattan Institute did not factor in the enormous numbers of illegal immigrants entering the US, a portion of the immigrant population that is overwhelmingly Mexican in origin.