A recent article looked into 16,000 PhD graduate students in 161 US chemistry departments, and showed that Chinese students outperformed their peers and were as well as awardees of the NSF doctoral fellowship program, in terms of scientific contributions (Patrick Gaule, Chinese Graduate Students and US Scientific Productivity, The Review of Economics and Statistics, Vol. 95, No. 2, Pages 698-701, May 2013). The study for the first time confirmed with scientific methods what people in the field had long known.
On the other hand, without green card on a short visa (shorter than most international students), and surrounded in sometimes unfriendly working environment with uncertain in their future life, the sorrow of Chinese graduate students had long been overlooked.
They have to battle with discrimination from those privileged and resentment from the bottom, and often take the least paid job, in additional to battling with a often conflicting culture. Systematic repression is abundant, too. In some labs, a Chinese student will be paired up with an American student, with the Chinese student works the work, and the US student press the button when it is necessary due to regulations put into place to prevent foreigners using certain lab equipments. In other occasion, Chinese are the only nationals who are forbidden from working in certain field. Many had quietly complained unable to graduate while being exploited as academic slavery, other were threatened of retaliation the moment they found a job offer.
With the rise of China economy, it should not be a surprise to see more Chinese graduate students returning to China, at the same time while less top level students coming the US, if the trend continues.