For years, one theory about the supply of engineering students has been that that the field suffers from poor retention of students, especially women.

New research, from overlapping research teams, challenges that view. In fact, the study found that while engineering retention varies widely by institution and is indeed low at some institutions, it is not significantly lower than other fields. And women – though a minority in these programs – are as likely as men to remain in them.

The research suggests another reason for the numbers of engineering students being lower than many academics (not to mention politicians) would like: Engineering is much less likely than other disciplines to attract students who have started as majors in other subjects.

Of students graduating with an undergraduate degree in social sciences, the study found that only about half started in that field. For the rest of the sciences, about 60 percent started that way. But 93 percent of engineering degrees are awarded to those who started there, suggesting only minimal “migration” into the field, the researchers noted.

The findings are based on the Multiple-Institution Database for Investigating Engineering Development, which features data on 70,000 engineering students from nine institutions in the Southeast over a 17-year period ending in 2005. The database is managed by Matthew Ohland, an associate professor of engineering education at Purdue University.

While the data rebut the idea of retention gaps holding back engineering enrollments, they don’t show a successful overall pattern in retention. The data in the study find that the nine institutions have retention rates, over eight semesters, of 66 percent to 37 percent.

The researchers argue that institutions with higher rates should be studied to find ways to emulate their practices. But overall, the authors argue the study suggests that the way to increase enrollments is to do better recruitment, and not just of freshmen.

In a statement, Ohland said that “a huge message in these findings is that engineering students are amazingly like those in other disciplines, but we need to do more to attract students to engineering programs.”

Given this finding, Ohland suggests that colleges look at policies that discourage transfer into engineering. For example, many colleges have multiple calculus courses, one for engineering and others for other fields. As a result, a business or biology student who becomes interested in engineering may be discouraged by the prospect of retaking calculus.

Some of the findings from the database analysis appeared last year in the Journal of Engineering Education. The other findings have been accepted for publication in the Journal of Women and Minorities in Science and Engineering.