Freshmen who have many of their courses taught by adjuncts are less likely than other students to return as sophomores, according to a new study looking at six four-year colleges and universities in a state system. Further, the nature of the impact of adjunct instruction varies by institution type and the type of adjunct used, the study finds. And in some cases, students taking courses from full-time, non-tenure track instructors or from adjuncts well supported by their institutions do better than those taught by other kinds of adjuncts.

The study -- published in the journal Educational Policy -- is likely to be closely scrutinized by adjunct activists, who sometimes see such research as “blaming the victim" in that such instructors lack the resources and job security that can allow many tenured faculty members to connect with students.

But the research could also be influential in that it goes beyond previous research in not treating all adjuncts alike, and in that it frames the issue very much around retention at a time that many policy makers are focusing on how to improve graduation rates. The authors note that the typical four-year college loses 26 percent of its students between the first and second years, and that about 60 percent of college students who fail to finish end their program in the first year -- suggesting that any push to improve retention and graduation rates must address factors that relate to first-year retention.

The authors of the study, who have written previously on adjunct instructors, are Audrey J. Jaeger, associate professor of higher education at North Carolina State University, and M. Kevin Eagan, a postdoctoral research fellow at the Higher Education Research Institute of the University of California at Los Angeles.

The six institutions they studied included one doctoral extensive institution, two doctoral intensive institutions, two master’s institutions and one baccalaureate institution. And in a significant difference from past analyses of adjuncts, the scholars had a large enough sample to examine the relationships between retention and having different kinds of adjunct instruction: from full-time, non-tenure track instructors, from graduate student instructors, and from “other” adjuncts (including part-time instructors, postdoctoral fellows and others). The study also tracked a number of other factors related to grades, finances and academic programs, so that the adjunct impact could be isolated. Multiple cohorts were used from each of the universities, and patterns were relatively consistent across cohorts.

Here are the findings (compared to those taught by tenure-track faculty members):

Doctoral extensive university: For every 10 percent increase in instruction by “other” adjuncts, the probability of a student coming back as a sophomore drops by 4 percent. For every 10 percent increase in instruction by graduate students, the probability of coming back drops by 3 percent. And while there was a slight negative impact associated with instruction by full timers, it was not statistically significant.

Doctoral intensive universities: In a difference from the other sectors, more adjunct instruction helps retention. A 10 percent increase in adjunct instruction results in a 3 percent increase in likelihood of retention if taught by “other” or full-time adjuncts, and a 2 percent gain for instruction by graduate students. (The positive impact led the authors to investigate these institutions further, and they found that these institutions provide more support to adjuncts than is the norm, in both orientations and professional development for their non-tenure-track instructors.)

Master’s institutions: Here a 10 percent increase in use of adjunct instructors resulted in a 7 percent decrease in first-year retention for “other” adjunct instruction, a 2 percent decline for graduate student instruction and a 3 percent reduction for those taught by full-time adjunct instructors.

Baccalaureate institution: This institution did not have graduate student instruction, and it saw a 2 percent decrease in odds of continuing for freshmen who saw a 10 percent increase in adjunct instruction (regardless of full-time or part-time status).

The authors write that these findings suggest a significant impact when considering the widespread use of adjuncts at these (and many other) institutions. At all but one of the institutions studied, the average freshman had more than 50 percent of credits earned from courses taught by an adjunct instructor of one of the three kinds identified. Students with typical (for their institutions) use of adjunct instructors would see between a 10 and 30 percent decrease in their odds of coming back as freshmen, compared to students taught by those on the tenure track, the authors note.

Jaeger and Eagan are clear in the summary of their findings that they are not suggesting that adjuncts are bad instructors, or that the key to success in retention is using fewer adjuncts. They stress the importance of looking at adjuncts as distinct groups, not as a monolithic one -- and the evidence in their study is consistent with those who say adjuncts do better with more courses at single institutions and where they are provided with more support.

At the same time, Jaeger and Eagan say that, looking at the data in their entirety, the impact of adjunct instruction is real and needs attention. They suggest that colleges consider having adjuncts teach more of a mix of courses, including upper division courses. And they suggest that colleges consider the use of policies that would get more tenure-track faculty members teaching freshmen.

And while they note that their research suggests the importance of looking at different types of adjuncts (for example, to focus on unique teaching issues that might face graduate students), they found that many colleges don’t have the data. Some institutions that the researchers had hoped to include in the study didn’t have the ability to look at different kinds of adjuncts, even though they used them.

Further, they note that because adjunct hiring is so decentralized -- with individual departments deciding which instructors to assign to which courses -- administrations may be unaware of the cumulative impact of these decisions: notably, that there are first-year students taking all of their courses from part-time instructors.

The bottom line, Jaeger and Eagan write: If state university systems want to get serious about improving retention, considering the use of adjunct hiring must be part of the discussion, and states need to consider that the savings they get from using lesser paid adjuncts may not justify the impact on retention.

Adjuncts have been critical of such work in the past, while praising work that questioned whether there is an adjunct impact on student success.

The blog of the American Federation of Teachers' Faculty and College Excellence campaign -- which works both to increase the share of courses taught by those on the tenure track and to improve working conditions for adjuncts -- offered some praise for the new study. The findings about how the adjunct impact was positive on the campuses where adjuncts receive more support, the blog said, "hold promise for both improving the working conditions of adjunct faculty and helping students succeed with their educational goals."

Maria Maisto, board president of the New Faculty Majority, a new national adjunct group, said she was encouraged to see the study note "that better support for adjuncts translates into better outcomes for students." Maisto said she would have liked to have seen more study of the nature of support that makes a difference.

While she said those findings suggested "respect for contingent faculty" that hasn't always been clear in earlier studies, she criticized the use of "dehumanizing" language, such as references to "exposure" to adjunct faculty members. "All of that contributes in its own way to perpetuating a culture that is unsupportive of contingent faculty," she said. Still, she added of the new study that "provided its findings are closely examined and limitations properly appreciated, this report does contribute to the effort to improve undergraduate education through the improvement of working conditions for the majority of faculty directly responsible for it."