almost 11,000 students took the Physics GRE in the three year period from summer 2000 until summer 2003. That leaves ~3600 students per year taking the GRE.
However, even this number may be a bit inflated, for purposes of competition to get into grad school. Some graduate schools require their students to retake the Physics GRE while they are in graduate school if they did not reach some minimum score. Also, this does not take into account the number of people who took the exam more than once.
Another thing is that there has been a longstanding dispute over administrations of the GRE in Asia. Most grad schools will frankly look much more favorably at a 90th percentile score for an exam taken in the US or Europe than a top score from Asia. (I have been the student rep of the admission commitee for a graduate program, so I saw this firsthand, and I was told that the "Asian correction" happens just about everywhere) So don't think you absolutely have to get above 90 percentile to get in the top schools (although it certainly helps