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Time to Completion of the Ph.D.: What Factors Make a Difference?

Concern over attrition rates has directed attention to factors that lengthen the time between entry into graduate study and completion of the doctoral degree. A study by the University of California of its own graduates from nine campuses between 1980 and 1988 considered several factors (Nerad 1991). Their impact was examined for men and women and for racial/ethnic groups. While the study provides information only on those who completed doctorates, it documents differences in factors believed to contribute to attrition.
Completion times average less for persons in science and engineering fields than for all doctorate recipients; arts and humanities graduates and those in professional schools take considerably longer.
Having dependents lengthens the time for completion of the doctorate. The additional time differs for men and women, however, and is greater for women than for men in some science and engineering fields. Dependents made only small differences in social sciences, with men and women about equally affected.
Financial resources to support graduate study also make a difference in completion times for all students. Those supported primarily by fellowships or loans, or by assistantships (either research or teaching), completed degrees in much less time than those relying on their own or other resources. For all disciplines, completion times for all doctorate recipients were 7 years for those with research assistantships and 11 years for those relying on their own or other resources.
The effect of different types of assistance is not the same for all groups or all disciplines. Differences across racial/ethnic groups between those receiving research assistantships and those relying on their own resources were somewhat greater in the physical sciences than in the social sciences. The amounts by which completion times in physical sciences were longer were 3.1 years for Asians, 2.9 years for whites, and 1.2 years for underrepresented minorities. In the social sciences, the racial/ethnic groups showed fewer differences within the field: Relying on one's own resources increased completion time by 2.7 years for Asians, 2.8 years for whites, and 2.4 years for underrepresented minorities.

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