 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 for 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 2009, 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 says, 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. Critics say American immigration policies are too restrictive. Representative Zoe Lofgren is a Democrat who represents parts of Silicon Valley in California. She spoke at a recent congressional hearing. While we once asked the brightest minds in the world to come and make their homes here, we now turn them away. Having educated and trained the world's best students in our universities, we no longer welcome them to enrich this nation. Some companies, including Texas Instruments, say it can take ten years for their foreign workers to become permanent residents. Darla Whitaker is a senior vice president at Texas Instruments. She says, this is not sustainable. It hurts our company and our industry, and it places burdens and stresses on our employees. The United States limits the number of immigrants from other countries on a country-by-country basis. Students from countries with large populations generally have to wait the longest for a green card or proof of permanent residency. A group called the National Foundation for American Policy says a highly skilled Indian worker could have to wait up to 70 years. Vivek Wah-wah studies immigrants who start their own companies. He says the United States needs to change its immigration policies. He says, if we don't keep these people, if we don't compete, we're going to lose. We're going to become a third world country, and they're going to become like us. For VOA Special English, I'm Carolyn Presuti. We have transcripts and MP3s of our programs, and now PDFs for e-readers at voaspecialenglish.com.