The NSF has released a study on US doctoral dissertations that can be identified as conducting interdisciplinary (science?) research. (NSF results here.) On the survey of earned doctorates, doctoral candidates were asked to identify their primary and secondary field of research. In 2008, 27% of respondents indicated that their research was interdisciplinary.
From Science magazine's report on the study:
It's an article of faith among science policymakers that interdisciplinary research is essential to address society's most pressing technological challenges, from energy independence to improved health care. But don't ask them to measure it. The National Academies' upcoming assessment of doctoral research programs, for example, asked departments what percentage of their faculty members were associated with other programs. But the data "aren't very satisfactory," says Charlotte Kuh, study director. Part of the problem is the fuzzy definition of an interdisciplinary program, she adds.
The standard for what counts as interdisciplinary is not set very high, since the fields are cut fairly finely and research that straddles closely related fields is counted as interdisciplinary. Thus, a research project in ecology and plant pathology counts as interdisciplinary. So does endocrinology and environmental toxicology. Thus, 81% of respondents in the biological sciences who considered their research to be interdisciplinary listed a secondary discipline in the same broad field as their primary discipline.
In other words, how much does the survey depend on students' perception of what counts as interdisciplinary? And what sort of meaning does it give to interdisciplinarity to count closely related fields as meeting a standard of interdisciplinarity. It seems to me that if there are obstacles to interdisciplinary research (and I think there are), these are less likely to make a difference when the fields in question are agricultural science and plant pathology than when they are atmospheric science and sociology. Yet, when we hear proclamations of the tough problems that interdisciplinarity will solve, they are more often like the latter than the former.
Again, from the Science News report:
NSF officials say the survey doesn't address the larger question of how difficult or easy it is for students to pursue interdisciplinary degrees, nor the extent to which senior faculty engage in interdisciplinary research themselves. An ongoing NSF survey of academic research piloted a question about how much is being spent on such activities, and where on campus the research takes place. But that proved to be a tough question for research administrators to answer, says one program manager, and the results may not be usable.