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Revised 7/28/06

View the Taxonomy List

In any assessment of doctoral programs, a key question is: Which programs should be included? The task of constructing taxonomy of programs is to provide a framework for the analysis of research-doctorate programs as they exist today, with an eye to the future. A secondary question is: Which programs should be grouped together across universities for purposes of comparison and what names should be given to these aggregations?


The construction of taxonomy inevitably confronts limitations and requires execution of somewhat arbitrary decisions. The taxonomy builds upon the previous studies, in order to represent the continuity of doctoral research and training and to provide a basis for potential users of the proposed analysis to identify information important to them. Those users include scholars, students, academic administrators as well as industrial and governmental employers. Furthermore, taxonomy must correspond as much as possible to the actual programmatic organization of doctoral studies. In addition, however, taxonomy must capture the development of new and diversifying activity. The Committee struggled with the frequent disparity among institutional nomenclatures, representing essentially the same research and training activities, as well as by the rise of interdisciplinary work. The Committee did its best to construct a taxonomy that reflected the way most graduate programs are organized in most research universities but realizes that there may be areas where the fit may not be perfect. We thought it would be useful to name sub-fields for fields in the taxonomy in order to provide a guide for program placement.

View the Taxonomy List with Sub-Fields

We recognize that scholarship and research in interdisciplinary fields have grown significantly since the last study. Some of this work is multidisciplinary; some is cross disciplinary or interdisciplinary. We could not devise a single standard for all possible combinations. Where possible, we have attempted to include acknowledged interdisciplinary fields such as Neuroscience, Biomedical Engineering, and American Studies. In other instances, we listed areas as emerging fields. Our goal remains to identify and evaluate inter-, multi-, and cross-disciplinary fields. Once they become established scholarly areas and meet the threshold for inclusion in the study established by this and future committees, they will be added to the list.

The initial basis for the Committee’s consideration of its taxonomy was the classification of fields used in the Doctorate Records File (DRF), which is maintained by the National Science Foundation (NSF) as lead agency for a consortium that includes the National Institutes of Health, U.S. Department of Agriculture, and National Endowment for the Humanities, and U.S. Department of Education. Based on these data, the Committee reviewed the fields included in the 1995 Study to determine whether new fields had grown enough to merit inclusion and whether the criteria themselves were sensible. In earlier studies, the criteria for inclusion had been that a field must have produced at least 500 Ph.D.s over the most recent 5 years and be offered by programs that had produced 3 or more Ph.D.s in the last 3 years in at least 25 universities. After reviewing these criteria, the Committee agreed that the field inclusion criterion should be kept, although a few fields in the humanities should continue to be included even though they no longer met the threshold requirement.

Recommendation 3.1: The quantitative criterion for inclusion of a field used in the preceding study should be, for the most part, retained—i.e., 500 degrees granted in the last 5 years.

The Committee also reviewed the threshold level for inclusion of an individual program and, given the growth in the average size of programs, generally felt that a modification was warranted. A minimal amount of activity is required to evaluate a program.

This parameter is modified from the previous study—3 degrees in 3 years—to account for variations in small fields. The 25-university threshold is retained.

Recommendation 3.2: Only those programs that have produced 5 or more Ph.D.s in the last 5 years should be evaluated.

Two fields in the humanities, Classics and German language and literature, had been included in earlier studies but have since fallen below the threshold size for inclusion in terms of Ph.D. production. Adequate numbers of faculty remain, however, to assess the scholarly quality of programs. In the interests of continuity with earlier studies and the historical importance of these fields, the Committee felt that they should still be included. Continuity is a particularly important consideration. In the biological sciences, where the Committee redefined fields, the fields themselves had changed in a way that could not be ignored. Smaller fields in the humanities have a different problem. A number of them are experiencing shrinking enrollments, but it can be argued that inclusion in the NRC study may assist the higher-quality programs to survive.

Recommendation 3.3: Some fields should be included that do not meet the quantitative criteria, if they were included in earlier studies.

The number of degrees awarded in a field is determined by the number of new Ph.D.s who chose that field from the Survey of Earned Doctorates based on the NSF taxonomy. However, there is no external validation that these fields correctly reflect the current organization of doctorate programs. The Committee sought to investigate this question by requesting input from a large number of scholarly and professional societies. Beginning in December 2002, the proposed taxonomy was also presented in a public Website and suggestions were invited. As of mid-June 2003, over 100 suggestions had been received, and both the taxonomy and the list of subfields were discussed with the relevant scholarly societies. The taxonomy was also used in the pilot trials, and although the correspondence was not exact, the pilot sites found a reasonable fit with their graduate programs. This taxonomy included new fields that had grown or been overlooked in the last study. It also reflected the continuing reorganization of the biological sciences. The taxonomy put forward by the Committee; compared with the taxonomy for the 1995 Study is found in table 3.1 of the methodology study.

Inclusion of the arts and sciences and engineering fields preserves continuity with previous studies. Inclusion of agriculture recognizes the increasing convergence of research in those fields with research in the traditional biological sciences and the legitimacy of the research in these fields, separate and independent of other traditional biological disciplines.

The biological sciences presented special problems. The past decade has seen an expansion of research and doctoral training in the basic biomedical sciences. However, these Ph.D. programs are not all within faculties of arts and sciences, which was the focus of the 1995 Study. Many of them are located in medical schools and were overlooked in earlier studies. The Committee sought input from basic biomedical science programs in medical schools through the Graduate Research Education and Teaching Group of the American Association of Medical Colleges to assure systematic inclusion the next time the study is conducted.