Csak egy érdekes, a H-1B-vel foglalkozó cikkre hívnám fel a figyelmet:
http://heather.cs.ucdavis.edu/itaa.real.html

Két idézet (bocs, angolul):

The length of time needed to get a green card has become so long that a
Georgetown University study estimated in the year 2000 that only 25% of
the H-1Bs working in the U.S. at that time would ever be able to get a
green card; the rest would have to return to their home countries.

.....

Since domestic high-tech students correctly perceive that they do not need
a PhD to work in this industry, most of them, including most of the top
students, forego graduate work and instead go straight to industrial work
after finishing their undergraduate degree. To make up for this
``deficit,'' universities admit large numbers of foreign students to their
PhD programs. The latter use their U.S. degrees as steppingstones to H-1B
visas and eventually green cards. In short, if there were no H-1B program,
the foreign students would not come to the U.S. for graduate study;
universities would find their graduate programs depopulated and they would
lose their grant monies.