Science magazine reports on a study (pay wall) of the pipeline for native-born scientists:
The findings suggest that the United States risks losing its economic competitiveness not because of a work force inadequately trained in science, as conventional wisdom holds, but because of a lack of social and economic incentives to pursue careers in science and technology.
Other reports, this one, e.g., suggest that top physics Ph.D.s are being lured to Wall Street to develop trading programs. Many months after the start of the banking crisis, a UCLA physics professor told me that many of his top graduates are still going to Wall Street.