According to GMAC, GMAT is designed as a predictor of prospective students' academic performance on MBAs and other graduate business studies programs. It is also designed on a comparative basis, so that schools can measure the relative abilities of prospective students, based on it's objectivity and consistancy.
In order to make sure that schools can verify this, GMAC runs a validity Study Service, allowing schools to gauge the value of the GMAT results against their GMAT scores. This continued monitoring of the value and relevance of GMAT makes sure that the business schools will continue to insist that prospective students use GMAT as a way in to their chosen MBA programs.
# posted by Mary @ 1:40 PM