Some interesting info in an article urging the US to liberalize its H1 visa regime:
Our economy depends heavily on skilled immigration. Half of research and development workers, one-quarter of doctors and nurses, and a quarter of all doctoral degree holders were born in other countries. Government and trade groups estimate that we need some 20,000 more doctors and 300,000 more nurses. Yet because only 140,000 employment-based visas are available each year, skilled workers can wait five years or more for a green card. Annual per-country visa caps make the wait even longer for high-migration countries like India and China, which send us many engineers and scientists, or the Philippines, which sends many nurses.