Information about attrition is available only at the department or program level, but the data that are available allow some broad comparisons of program completion rates among fields and disciplines within fixed periods of time (eight years in the case of the humanities, six years in the other disciplines).
The findings below refer to the “median program completion rate” for a particular field or discipline. For each field, this rate is the percentage of completions reported by the program within the field whose completion rate falls in the middle of the range of rates reported by all programs in the field. Thus, half of the remaining programs in the field/discipline had a lower completion rate, and half had a higher a completion rate.
Findings and Trends  Completion rates for humanities doctorate programs are similar to those for programs in the mathematical and physical sciences (Indicator II17a). The median program completion rate for both fields was 42%.^{[1]} (Click the “About the Data” button under the graph for important details about how these figures were calculated.)
 Engineering and biological and health science programs had the highest median program completion rates, 50%. The lowest median program completion rate was found among behavioral and social science programs (35%).
 Median completion rates for humanities programs varied considerably by discipline (Indicator II17b). Theater and performance studies programs had the highest median completion rate, with 56% of students in the median program completing their Ph.D.’s within eight years. Languages, societies, and cultures programs had a median completion rate of 33%, the lowest recorded within the humanities field.
 History and English language and literature programs, two of the most common types of humanities programs, had median completion rates of 42% and 46%.
 The span of “typical” completion rates among programs in particular humanities disciplines differed widely. The completion rates of German programs were clustered relatively tightly around the median, for an interquartile range (IQR) of 20, the lowest of all the disciplines. In contrast, typical completion rates for French programs, those with the highest IQR, ranged from 17% to 64%. (See Indicator II7b’s “About the Data” for an explanation of IQR.)
II17a: Completion Rates for Doctorate Programs in the Humanities and Other Selected Fields for Students Entering 1996–1997 to 2005–2006*   * A “completer” is defined as a student who obtains his or her Ph.D. within eight years of entering a doctorate program (for humanities programs) or six years (for programs in other fields).
Source: National Research Council, Committee to Assess ResearchDoctorate Programs, “A DataBased Assessment of ResearchDoctorate Programs in the United States: Data Table in Excel (2010).” An explanation of how each program’s Ph.D. completion rate was calculated is included under the “Guide” tab of the Excel workbook. 
 

II17b: Completion Rates for Doctorate Programs in the Humanities for Students Entering 1996–1997 to 2005–2006, by Discipline*   * “Completion” is defined as a student who obtains his or her Ph.D. within eight years of entering a doctorate program (for humanities programs) or six years (for programs in other fields).
Source: National Research Council, Committee to Assess ResearchDoctorate Programs, “A DataBased Assessment of ResearchDoctorate Programs in the United States: Data Table in Excel (2010).” An explanation of how each program’s Ph.D. completion rate was calculated is included under the “Guide” tab of the Excel workbook. 
 

Endnotes^{[1]} Doctorate programs at participating institutions were asked by the NRC to report the number of “graduate students who entered in different cohorts from 1996–1997 to 2005–2006 and the number in each cohort who completed in 3 years or less, in their 4th, 5th, 6th, 7th, 8th, 9th years, and in 10 or more years. To compute the completion percentage, the number of doctoral students for a given entering cohort who completed their doctorate in 3 years or less and in their 4th, 5th, 6th years were totaled and the total was divided by the entering students in that cohort. This computation was made for each cohort that entered from 1996–1997 to 1998–1999 for the humanities and 1996–1997 to 2000–2001 for the other fields. Cohorts beyond these years were not considered, since the students could complete in a year that was after the final year 2005–2006 for which data were collected. To compute the average completion percentage, an average was taken over 3 cohorts for the humanities and over 5 cohorts for other fields” (National Research Council, Committee to Assess ResearchDoctorate Programs, “A DataBased Assessment of ResearchDoctorate Programs in the United States: Data Table in Excel (2010),” http://www.nap.edu/rdp/, under “Guide” tab in Excel workbook). About the Data The values reported here are for responding doctorate programs in a given field (or discipline), not the student population in that field.
The attrition data presented by the Humanities Indicators come from a comprehensive assessment of U.S. researchdoctorate programs administered by the National Research Council (NRC) and funded by the National Institutes of Health, the National Science Foundation, the Alfred P. Sloan Foundation, the Andrew W. Mellon Foundation, and participating universities. The assessment involved the collection of a variety of data on doctorate programs, including Ph.D. completion rates. These data were then used to develop multidimensional ratings of programs at approximately 200 institutions of higher learning (see http://sites.nationalacademies.org/pga/Resdoc/index.htm for more information about the project).
Doctorate completion was defined by the NRC as obtaining a degree within eight years of entering a Ph.D. program for students in the humanities and within six years for students in other fields. Indicator II15, Years to Attainment of a Humanities Doctorate, reports, during the time period covered by NRC study, the median number of years it took students to earn a humanities doctorate was approximately 10. Thus the completion rate for humanities programs calculated by the NRC does not include a substantial number of students who go on to obtain Ph.D.’s in the humanities.)
This indicator uses the interquartile range (IQR) to describe doctorate program completion rates in the humanities and several other fields. The IQR is widely used as a means of describing the “typical” or “usual” values exhibited by a group and ignores the most extreme values of a particular variable (in this case, doctorate program completion rate). Quartiles are statistics that divide the observations in a batch of numeric data into several groups, each of which contains 25% of the data. The lower, middle, and upper quartiles are computed by ordering the values for a particular variable from smallest to largest and then finding the values below which fall 25% (the lower quartile), 50% (the middle quartile), and 75% (the upper quartile) of the data. The lower quartile and the upper quartile are the two values that define the interquartile range. The middle quartile is also known as the median. As shown in this graph, in the humanities as well as the mathematical and physical sciences, the middle half of the programs graduated from slightly more than 25% to 55% of their students within the anticipated number of years (i.e., eight years for students of the humanities, six years for science students). About the Data The values reported here are for responding doctorate programs in a given field (or discipline), not the student population in that field.
The attrition data presented by the Humanities Indicators come from a comprehensive assessment of U.S. researchdoctorate programs administered by the National Research Council (NRC) and funded by the National Institutes of Health, the National Science Foundation, the Alfred P. Sloan Foundation, the Andrew W. Mellon Foundation, and participating universities. The assessment involved the collection of a variety of data on doctorate programs, including Ph.D. completion rates. These data were then used to develop multidimensional ratings of programs at approximately 200 institutions of higher learning (see http://sites.nationalacademies.org/pga/Resdoc/index.htm for more information about the project).
Doctorate completion was defined by the NRC as obtaining a degree within eight years of entering a Ph.D. program for students in the humanities and within six years for students in other fields. Indicator II15, Years to Attainment of a Humanities Doctorate, reports, during the time period covered by NRC study, the median number of years it took students to earn a humanities doctorate was approximately 10. Thus the completion rate for humanities programs calculated by the NRC does not include a substantial number of students who go on to obtain Ph.D.’s in the humanities.)
This indicator uses the interquartile range (IQR) to describe doctorate program completion rates in the humanities and several other fields. The IQR is widely used as a means of describing the “typical” or “usual” values exhibited by a group and ignores the most extreme values of a particular variable (in this case, doctorate program completion rate). Quartiles are statistics that divide the observations in a batch of numeric data into several groups, each of which contains 25% of the data. The lower, middle, and upper quartiles are computed by ordering the values for a particular variable from smallest to largest and then finding the values below which fall 25% (the lower quartile), 50% (the middle quartile), and 75% (the upper quartile) of the data. The lower quartile and the upper quartile are the two values that define the interquartile range. The middle quartile is also known as the median. As shown in this graph, in the humanities as well as the mathematical and physical sciences, the middle half of the programs graduated from slightly more than 25% to 55% of their students within the anticipated number of years (i.e., eight years for students of the humanities, six years for science students).
