This might answer your question.
Retrieved from the November 24, 2009 post on Manhattan GMAT
"For the first time, non-U.S. citizens (135,105) outnumbered U.S. test-takers (130,508). This is likely because of the increasing adoption of the GMAT by international business schools, which are themselves increasing in number. If historical trends continue, this may continue to skew the GMAT’s math curve up (a subset of international applicants tends to be very good at math) and the verbal curve down (a subset of international applicants tends to be poor at verbal)."