Why and When Ph.D. Students Finish

New data point to importance of money and mentors -- and to significant differences by discipline.
July 17, 2007

Why do some graduate students seemingly zip through programs, straight to the Ph.D., while others languish for a decade or even longer? Or never finish?

These questions are at the root of the Council of Graduate Schools' Ph.D. Completion Project, which aims to study these issues, identify promising practices, and identify strategies so that more graduate students finish their programs in a timely way. On Monday, the council released preliminary data it gathered from surveys of graduate students who earned their Ph.D.'s, and data on completion rates by disciplines. The results come from 29 of the universities participating in the Ph.D. Completion Project, which involves both public and private universities, elite and up-and-coming institutions alike.

The results reinforce the belief about the role of money in promoting completion. Those who finished up their doctorates ranked financial issues as the top factor in enabling them to do so. And to the extent the data show differences among disciplines in financing, those differences carry over to rates of completion (humanities students need to borrow more, and take longer to finish).

With regard to the "main factors" contributing to completion, new Ph.D.'s (who could pick more than one item that applied) ranked the following: 80 percent cited financial support, 63 percent mentoring/advising, 60 percent family support, 39 percent social environment and peer support, 39 percent program quality, and 30 percent professional and career guidance.

Humanities Ph.D.'s were more likely to have held fellowships and teaching assistant positions than were those in other fields, while those in engineering, mathematics and physical sciences were more likely to hold research assistantships. But factors other than merely holding fellowships -- possibilities include their size and duration -- are also clearly in play as the data show a significant gap in borrowing by graduate students who finish their Ph.D.'s.

Percentage of Ph.D. Completers Who Received Loans for Doctoral Study, by Field

Field % With Any Loans % With at Least $35,000 in Loans
Engineering 19% 12%
Life sciences 26% 18%
Math and physical sciences 24% 20%
Social sciences 50% 35%
Humanities 47% 38%

If finances pointed to differences among disciplines, other questions in the survey found common ground. Those who finished their Ph.D.'s were asked about the subject of valuable advice they received from mentors. Research was by far the top topic (and people could pick more than one), across all fields. Teaching was much less likely to be cited. Career advice varied, with it being cited in the humanities and social sciences much more than in other fields.

Most Valuable Advice Ph.D. Completers Reported From Mentors, by Field

Field Teaching Research Careers Other Topics
Engineering 41% 90% 47% 13%
Life sciences 50% 86% 63% 11%
Math and physical sciences 49% 93% 58% 7%
Social sciences 48% 83% 71% 20%
Humanities 51% 77% 74% 18%

Across disciplines, those who finished their Ph.D.'s said that their academic advisers were most available to them early in their graduate careers. Asked if their advisers were "readily" available to meet with them during various stages of their doctoral education, the answers were 80 percent for coursework, 63 percent for qualifying exams, 60 percent for preliminary exams, 39 percent for the dissertation preparation, and 39 percent for the dissertation defense.

Previous studies by various groups have found that time-to-completion rates for humanities fields lag those for others, and the Council of Graduate Schools effort provided more confirmation. In the physical and biological science and technology fields, more than half of those in entering cohorts are earning a doctorate between year six and seven of a program. In the social sciences, year seven sees only a completion rate of just over 40 percent; in the humanities the figure is 29 percent.

Cumulative Completion Rates for Cohorts Entering 1992-4, by Fields

Field Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10
Engineering 6.8% 16.7% 34.5% 48.8% 57.4% 61.6% 63.3% 64.4%
Life sciences 4.4% 9.8% 22.2% 42.5% 54.6% 60.5% 62.9% 63.8%
Math and physical sciences 2.6% 9.1% 23.4% 39.3% 48.1% 52.1% 53.8% 54.7%
Social sciences 6.7% 11.5% 20.5% 31.1% 40.9% 47.5% 52.6% 55.7%
Humanities 2.9% 6.2% 11.8% 19.6% 29.0% 36.7% 44.4% 49.1%

Within the broad disciplinary categories, rates were not uniform. Civil engineers complete at higher rates than electrical engineers. Chemistry's rates are higher than mathematics. In the humanities, 10-year completion rates are fairly similar across disciplines, but at the six- and seven-year marks, philosophy and foreign languages and literatures outpace English and history.

Daniel Denecke, program director for the council's Ph.D. completion efforts, said that the next stages of the project will focus on figuring out what the data mean. He said that a first reaction would be to focus on funds. "A lot of these line up on funding," he said, with regard to disciplines and financial support.

But other factors are also in play and a higher attrition rate may reflect the availability of good jobs in some fields for people with master's degrees, not flawed doctoral programs. "We're going to be looking at all kinds of factors," he said.


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