This is the VOA Special English Education Report.

Congress is studying how to change immigration policies in an effort to get more foreign students to stay and work in the United States. Many foreign students come to the United States to earn advanced degrees in science, technology, engineering and math. But many are unable to get a visa to live and work here after they graduate.

In two thousand nine, foreign students earned up to two-thirds of the physics and engineering doctorates awarded by American colleges and universities.

Xiao Qin from Beijing is studying for a PhD in computer science at Georgetown University in Washington. He would like to work for Google, Yahoo or Microsoft.

XIAO QIN: "Obviously, we prefer to stay here for several years, but if we cannot get any valid visa we have to leave."

So far no agreement has been reached on how to stop this so-called reverse brain drain. The loss of highly skilled workers usually involves developing countries losing them to wealthier ones.