Among the more fascinating facts discovered in Brookings analyst Neil Ruiz's research on the geography of foreign students in the U.S. is where they decide to stay after they get their degree.

A plurality stay in New York City — or move there.

New York, it turns out, is very sticky. Foreign students are more likely to stay in New York City after graduation than anywhere else in the country. We all love New York, and it's the biggest city in the country, but there's no reason why it should be so magnetic, unless the city (and New York state) do things to make it attractive for foreign students to stay there after they study. And indeed, they do.

Other high-ranking "sticky" cities: Honolulu, Miami, Seattle, and Las Vegas.

(The places that F1 visa holders were anxious to get away from: Erie, Pennsylvania; Binghamton, New York; and Port Arthur, Texas.)

Las Vegas is not especially fun for "locals," but I think the anomaly can be explained by two factors: Clark County's very vigorous attempt to lure these students and the University of Nevada-Las Vegas's hotel management program being complemented by the presence of hotels there.

In Honolulu, Ruiz's research suggests, the students are in tourism-related fields. In Seattle, the lure is the IT/computer industry, and so are the foreign students there. (A majority are studying science and technology.)

Here in Los Angeles, there is no "magnet" industry, but there is a big diversified metro area to look for work in. A plurality of students are getting degrees in business and marketing there, and a large number want to break into the entertainment industry. L.A. ranks sixth highest in terms of retaining students. L.A. is not at all a destination for STEM visa folders: the city ranks 98th of the 118 metropolitan areas Ruiz studied.

What does this all mean?

First, it's very hard for even talented students to get a green card. There are numerical limits in law and financial limits in reality. Many businesses won't sponsor even great potential long-term employees for green cards because it costs them too much.

The students who manage to get visas have incentives to be choosy about where they live.

Ruiz says that cities can retain more foreign students if they acknowledge their presence, work to integrate them into the community, and create links between their home countries and their current place of residence.

I would guess that nativism and economic worries also play a role, especially in smaller cities and towns, where the presumption is that American citizens ought to get the good jobs and foreign students shouldn't crowd them out.

But Ruiz's research suggests that, on a macro level, foreign students are very productive and contribute far more to the U.S. economy than they might take away when those who return to their native countries stop living here.

His research also highlights the emerging phenomenon of "green card mills" and the cities that feed them. Hyderabad, the locus of computer engineering in India, sends tens of thousands of students to niche technical schools here and gets them right back after graduation. Had you heard of Herguan University? International Technology University? Stratford University? Tri-Valley University? The University of North Virginia? Neither had I. But they amount to diploma mills for aspiring Indian engineers and computer scientists.