Women have continued to increase their presence as members of the faculty at institutions of higher education over the past few decades. Based on the National Science Foundation's Survey of Earned Doctorates, the 2001-02 academic year marked the first time that more women received doctoral degrees than men. In addition, the U.S. Digest of Education Studies reported that 63 percent of graduate students in 2007 were women. Despite such progress, female faculty members continue to be clustered in lower ranks, work at less prestigious universities, and earn less than their male colleagues. A variety of explanations have been offered through numerous studies in recent years in an attempt to gain a better understanding of the disparities.