In terms of completion rates, the average percent of doctoral students who complete their degrees in 6 years or less ranges from 42 percent in genetics and genomics to 56 percent in pharmacology, toxicology, and environmental health. There is substantial variation among programs, however. For example, in immunology and infectious disease, one university had a completion rate of 100 percent, while another had a completion rate of 25 percent, although both programs average 3.4 doctorates per year. The extent to which this difference is due to variations in admissions policies, retention efforts, funding, or other factors, is impossible to say. Case studies or other detailed analyses would be needed to sort this out. It is noteworthy, however, that immunology and infectious disease programs at both institutions had the same median time to degree for those students who did complete.

As might be expected, a shorter median time to degree is correlated with a higher completion rate. In at least six fields the coefficient is < -0.3:

TABLE 4-2 Correlations Between Median Time to Degree and Average Completion Rate by Field


Field Median Time to Degree (years) Average Completion Rate (%) Correlation
Biochemistry, Biophysics, and Structural Biology 5.63 45.9 -0.375
Biomedical Engineering and Bioengineering 5.06 46.3 -0.134
Cell and Developmental Biology 5.66 50.1 -0.383
Genetics and Genomics 5.73 41.6 -0.451
Immunology and Infectious Disease 5.36 56.2 -0.071
Integrated Biological and Biomedical Sciences 5.62 47.4 -0.362
Microbiology 5.58 47.1 -0.493
Neuroscience and Neurobiology 5.68 46.2 -0.464
Nutrition 4.88 55.8 -0.165
Pharmacology, Toxicology, and Environmental Health 5.21 56.1 -0.260
Physiology 5.13 50.9 -0.179

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement