The country is in the midst of what most scholars refer to as the "modern wave" of immigration, which started when Congress passed the Immigration and Nationality Act of 1965. This law essentially opened the door to Latin Americans, Africans, and Asians who had previously been barred by an immigration quota system that gave preference to northern Europeans. Since then, 40 million immigrants have come to the US, reports the Pew Research Center.
In sheer numbers there are more immigrants today than in prior generations, but as a percentage of the population, first- and second-generation immigrants peaked in the early part of the 20th century. In 1900, 34.5 percent of the US population was first or second generation; last year it was 24.5 percent.
Today, census data show, 12 million immigrants come from Mexico and 10 million hail from South and East Asia. Almost 4 million come from the Caribbean, while 14.5 million come from Central America, South America, the Middle East, and elsewhere. Within those groups, of course, there are huge differences; that "elsewhere" category, for instance, includes hundreds of thousands from countries ranging from the United Kingdom to Nigeria to Bosnia-Herzegovina.
Categorizing the assimilation of all these different people, Professor Vigdor and the others knew, could prove a daunting task. Even the word itself – "assimilation" – had become contentious; in academia it was associated with nativist pressures on newcomers to assume Anglo sensibilities at the expense of their own culture and history.
But as a social scientist, Vigdor was eager to find evidence in an emotion-laden debate. The key, he says, is in census data.
"When you talk to some people about immigration today, they say, 'Well, my grandmother came here in 1902, and she learned to speak English, and she did all these things, and the immigrants today aren't doing it,' " Vigdor says. "And as it turns out, we were able to get a good sense of whether all the grandmas were really like that."