Trends in Interdisciplinary Dissertation Research: An Analysis of the Survey of Earned Doctorates
Prevalence of Interdisciplinary Doctoral Research
The 2001–08 waves of the Survey of Earned Doctorates contain 310,470 cases with valid codes for dissertation research fields. Of these, 88,293 reported more than one doctoral research field. This means that 28.4% of those earning doctorates from 2001–08 conducted interdisciplinary dissertation research. Table 1 documents the number of respondents who reported multiple dissertation fields each year from 2001 to 2008. The percentage of respondents who reported two or more fields was relatively similar across years. It ranged from a low of 27.7% in 2003 to a high of 30.0% in 2005. Therefore, there is no clear trend of increases or decreases in the rate of interdisciplinary dissertation research across this time period. Also, it does not appear that the change in question wording had much of an effect on the overall percentage of respondents reporting two or more fields.
SOURCE: National Science Foundation/National Center for Science and Engineering Statistics, Survey of Earned Doctorates.
 Although the Survey of Earned Doctorates first began allowing multiple responses to the dissertation research fields question in 2001, some individuals who were awarded doctorates in 2001 or later years filled out older versions of the questionnaire that did not allow for multiple responses. There are a total of 316,645 cases with valid data for a primary field of research in the 2001–08 data, but 6,175 of these respondents (just about two percent) completed a 2000 or earlier questionnaire. Most of the respondents who submitted an earlier version of questionnaire were 2001 graduates, but there were also small numbers of 2002–08 graduates who utilized a pre-2001 version as well. Due to the nature of the questions addressed in this working paper, theses analyses are limited to only those 2001–08 graduates who completed a 2001 or later version of the questionnaire. Therefore, they are not completely representative of all 2001–2008 graduates.