this data comes from a WSJ piece published earlier this year
Most foreigners who came to the U.S. to earn doctorate degrees in science and engineering stayed on after graduation—at least until the recession began—refuting predictions that post-9/11 restrictions on immigrants or expanding opportunities in China and India would send more of them home. 62% of foreigners holding temporary visas who earned Ph.D.s in science and engineering at U.S. universities in 2002 were still in the U.S. in 2007, the latest year for which figures are available. Of those who graduated in 1997, 60% were still in the U.S. in 2007, according to the data compiled by the U.S. Energy Department’s Oak Ridge Institute for Science and Education for the National Science Foundation. Foreigners account for about 40% of all science and engineering Ph.D. holders working in the U.S., and a larger fraction in engineering, math and computer fields. “Our ability to continue to attract and keep foreign scientists and engineers is critical to…increase investment in science and technology,” Oak Ridge analyst Michael Finn said.  Other analysts see signs that recent foreign grads are increasingly likely to return home,  in today’s weak job market. “I have no doubt that the 2009 data will show a dramatic shift,” said Vivek Wadwha, executive in residence at Duke University’s Pratt School of Engineering, who has been warning loudly about the threat that trend would pose to innovation in the U.S. In October 2008, Mr. Wadwha and others used Facebook to question 1,224 foreigners studying at U.S. institutions at all levels. More than half the Indians and 40% of the Chinese said they hoped to return home within five years.