Trends in Interdisciplinary Dissertation Research: An Analysis of the Survey of Earned Doctorates
The Survey of Earned Doctorates
The Survey of Earned Doctorates is conducted annually by the National Science Foundation to collect data on the number of individuals receiving research doctorates in the United States. All individuals who are finishing a research doctorate in any field at an accredited U.S. institution are asked to complete the survey, which collects information about individuals’ degrees, academic institutions, educational finances, postgraduation plans, and demographic characteristics.
The Survey of Earned Doctorates asks respondents to report the field or fields of study that represent their dissertation research. They are asked to write in the name of the field or fields and then enter in a corresponding three-digit code from a provided list. Beginning in 2001, respondents were given the option of reporting both a primary as well as a secondary field, if applicable. The question from the 2001–03 surveys read as follows:
In 2004 the wording of the question was changed. The new question explicitly incorporates the term "interdisciplinary":
Beginning in 2004, respondents could then also indicate two additional fields (for a total of four fields, if applicable). Both forms of this question used since 2001 are possible indicators of interdisciplinary dissertation research. That is, if respondents provide two or more fields, this suggests that they may have conducted interdisciplinary research. For the purposes of the analyses in this report, we considered dissertation research for a doctoral degree to be interdisciplinary if the respondent reported more than one field of dissertation research. In this report, we examined data from the 2001–08 Surveys of Earned Doctorates to assess the trends in the reporting of interdisciplinary doctoral research. This analysis used the best available source of data on interdisciplinary researchers to provide us with a comprehensive view of the prevalence of interdisciplinary activities at the doctoral level.
 In this report, we relied upon only the numerical codes reported by respondents for each field. All of the following analyses are limited to respondents who reported a valid dissertation field code for at least their primary field of dissertation research. Respondents were excluded if they did not write a dissertation, were missing information about their dissertation, or did not indicate field codes for their dissertation.
 In a separate question, the Survey of Earned Doctorates also asks respondents to indicate the field in which their doctoral degree was awarded. The field of their degree does not necessarily match the primary field of their dissertation research. However, these two indicators are very highly correlated (p = 0.97). For the sake of simplicity, we refer to respondents' primary fields of dissertation research as their doctoral fields, although it is noted that there are some cases where these two codes do not coincide.