On Thursday, we knew nothing of the Tsarnaev brothers. By today, a rich portrait has emerged. The elder brother, Tamerlan, was having difficulty establishing himself in the United States. He reportedly complained of having few friends, and had problems gaining traction in his chosen career or as a student. In the course of his difficulties he turned to Islam. By all accounts, he was the more radicalized of the two brothers.
The younger brother, Dzhokhar, appeared to be on a very different trajectory. Socially, he had been reasonably well integrated into his high school. Educationally, he had made the transition to a four-year public university. He was a naturalized citizen of the United States.
There are undoubtedly thousands of potential factors that could explain the difference in the two brothers' trajectories. But here's a factoid of some importance. Dzhokhar, according to reports, arrived in the United States at the age of 9; Tamerlan was 16.
The graph below is taken from my book, From Immigrants to Americans. It shows the English-language skills of immigrant adults in the United States as a function of the year they first arrived in the country. By all reports, the Tsarnaev brothers were fluent English speakers, so don't read the graph literally. Think of the ability to speak English as a signal that an immigrant "fits in," to use words attributed to Tamerlan himself.
Immigrants who arrive as young children are overwhelmingly likely to speak English fluently as adults. They are educated and socialized in American schools, and along many other dimensions are difficult to distinguish from native-born adults.
There is a pronounced difference between immigrants who arrive with an age in the single digits and those who arrive in the teenage years. The latter group is perhaps only half as likely to speak English fluently. Again, don't read this as an analysis of language alone, but rather an analysis of factors associated with blending into American society. Immigrants who arrive in the teenage years enter a different educational and social world. Resources to support them are harder to come by; friendship circles are more fully established and harder to penetrate. By this measure, immigrants who arrive in their late teenage years are even worse off than those who arrive in their twenties.
As I suggested in my last post, there really is no viable policy option for screening out immigrants who will cause problems ten years down the line. A truly comprehensive immigration policy is about more than keeping the "wrong" people out. Society's stake in immigration depends on what migrants do after they arrive, not just whether they arrive, and the policies we adopt steer behavior in both intended and unintended ways.
As a simple example, consider naturalization policy. Developed countries vary dramatically in terms of the ease and requirements for becoming a citizen. In the United States, a green card holder faces a five-year wait for citizenship. The wait is shorter in Canada and quite a bit longer in many European countries. Unsurprisingly, the nations with longer waits have more profound problems integrating immigrants into their societies. Ask yourself this: if you wanted to minimize the risk of creating a disaffected class of legal residents in this country, would you raise or lower the waiting period? You might ask similar questions about permitting people to be "guest workers" with no path to legal citizenship, or registered provisional immigrants with only a tortuous path.
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