Greg Mankiw makes an interesting point.
Two-thirds of doctoral candidates in science and engineering in U.S. universities are foreign-born. But only 140,000 employment-based green cards are available annually, and 1 million educated professionals are waiting — often five or more years — for cards. Congress could quickly add a zero to the number available, thereby boosting the U.S. economy.
But maybe a much more interesting question is what is wrong with our incentive system that two-thirds of doctoral candidates are foreign born? Why aren’t more native born Americans interested in earning a doctorate in science or engineering? Is it comparable to stoop labor in the agricultural sector where firms do not pay enough to attract domestic labor? Obviously, Americans must think they have better alternatives.