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."
As early as 1900, the US Census was asking people about where they were born and when they had arrived in the US. Using these markers, as well as other data points such as homeownership, marital status, and citizenship, Vigdor created an index that calculated a statistical difference between immigrants and native-born Americans. Full assimilation, according to Vigdor's work, is when these data points are indistinguishable.
"Assimilation is a process whereby people come to adopt the various mannerisms and behavior of native-born residents of a country...," Vigdor says. "By being able to track immigrants as they spend more time in the US, we can trace out how that process works. And the process actually works in a remarkably similar manner whether you're looking over the past 20 years in the US or looking at immigration from Eastern Europe at the turn of the last century."