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Technical Notes

Data presented in Doctorate Recipients from U.S. Universities: 2013 were collected by the Survey of Earned Doctorates (SED). The survey is sponsored by six federal agencies: the National Science Foundation (NSF), National Institutes of Health (NIH), U.S. Department of Education (USED), U.S. Department of Agriculture (USDA), National Endowment for the Humanities (NEH), and the National Aeronautics and Space Administration (NASA). This report presents the summary of these survey data.

Survey Eligibility

The SED collects information only on research doctorate recipients. Research doctoral degrees prepare students to make original intellectual contributions in a field of study. Research doctorates require the completion of a dissertation or equivalent project and are not primarily intended for the practice of a profession. The SED recognized 18 distinct types of research doctorates in 2013 (table A-1). Professional degrees, such as the MD, DDS, DVM, JD, PsyD, and DMin, are not covered by the survey.

The doctor of philosophy (PhD) constitutes the vast majority of research doctoral degrees. Of the 52,760 new research doctorates granted in 2013, 97.7% were PhDs; PhDs were 97.9% of research doctorates in 2012 (table A-2). The next most frequently occurring type of research doctorate was the doctor of education (EdD), which accounted for 1.3% of the total in 2013. No other type of doctoral degree accounted for as much as 0.5% of the new research doctorates in 2013.

Survey Universe

The population eligible for the 2013 survey consisted of all individuals who received a research doctorate from a U.S. academic institution in the 12-month period ending 30 June 2013. The total universe consisted of 52,760 persons in 421 institutions that conferred research doctorates in 2013.

Data Collection

Paper copies of the survey instrument were mailed and the Web survey link was distributed electronically to institutional coordinators at the doctorate-awarding institutions. The institutional coordinators distributed the survey forms or the Web link to individuals receiving a research doctorate. Data were also collected using the telephone version of the survey. Respondents who did not complete critical survey items were contacted by e-mail or postal mail to request responses.

A small but growing number of research doctoral degrees are awarded as a part of joint doctoral programs (i.e., a research doctorate recipient studied at more than one institution in pursuit of the doctoral degree). In these instances the survey contractor relies on information provided by the institutions to appropriately attribute the doctorate to one of the doctorate-granting institutions.

The survey collects a complete college education history. To code the undergraduate institutions of respondents from foreign countries, survey staff use the coding manual Mapping the World of Education: The Comparative Database System, augmented with over 3,000 additional institutions from the Europa World of Learning. About one-third of U.S. doctorate recipients received undergraduate degrees from foreign institutions [1].

NORC at the University of Chicago currently conducts the survey under contract to NSF.

Survey Response Rates

Ninety-two percent of the 52,760 individuals who received a research doctorate in 2013 completed the survey instrument (table A-3). This percentage is referred to as the self-report rate in this report. Limited records (field of study, doctoral institution, and sex) are constructed for nonrespondents from administrative records of the university—commencement programs, graduation lists, and other public records—and are included in the reported total of 52,760 doctorate recipients for 2013.

Nonresponse was concentrated in certain institutions: 1% of the 421 doctorate-granting institutions accounted for 20% of the total nonrespondents, and 10% of these institutions accounted for 68% of the total nonrespondents.

Counts for previous years were corrected by the addition of data from surveys received after the close of data collection for a given year.

Table A-4 shows item response rates for 2003–13 by variable name (see clarifying notes in table A-4).

Disclosure Protection

Two strategies are used in this report to protect against the disclosure of confidential information provided by SED respondents. In the first, used since 2004, data cell values based on counts of respondents that fall below a predetermined threshold are deemed to be sensitive to potential disclosure and are suppressed. The symbol “D” replaces the cell value. If a suppressed cell does not provide sufficient protection in tables that include marginal totals, additional (complementary) suppressions of above-threshold data cells are necessary, and the suppression symbol “D” is used to replace those cell values as well.

The second disclosure protection strategy, field aggregation, was first applied in Doctorate Recipients from U.S. Universities: Summary Report 2007–08. Field aggregation was applied to data tables 16 and 22 in the current report, which present counts of doctorate recipients classified by fine fields of degree and by either sex (table 16) or race and ethnicity (table 22). Because some fine fields of degree award relatively few doctorates in a single year, the degree counts by race, ethnicity, or sex within these fields can be quite small, leading to extensive cell suppression. The field aggregation technique combines data from small fields of degree with the data from related fields, so that the degree counts in the aggregated fields are sufficiently large to protect the confidentiality of respondent information.

Data by race, ethnicity, and sex by the fine fields shown in tables 16 and 22 are reported for fields in which at least 25 U.S. citizen or permanent resident individuals earn a doctoral degree in a given year, regardless of how small the count may be in a particular cell. Counts of doctorate recipients in fields having fewer than 25 U.S. citizen or permanent resident doctorates awarded are aggregated with those of one or more related fields until the total number of doctorates in the aggregated field reaches at least 25 U.S. citizens and permanent residents. The degree count in each racial, ethnic, or sex category of these aggregated fields is reported in tables 16 and 22, but the constituent fine fields of the aggregated fields are not displayed.

In 2013, fewer than 25 doctorates were awarded in 79 of the 317 fine fields of degree. These below-threshold fields were combined with 66 related fields of degree to produce 44 aggregated fields in 2013. Tables 16 and 22 report data on the 44 aggregated fields and the remaining 172 unaggregated fine fields. Table A-5 lists the aggregated fields that appear in tables 16 and 22 and identifies their constituent fine fields.

Changes to Survey Variables Over Time

Citizenship. The citizenship status variable is used to identify the appropriate citizenship category of respondents, including the citizenship category of respondents who did not respond to the citizenship status survey item on the SED. The code framework for the citizenship status variable is outlined below.

CodeCitizenship category
0U.S. native born
1U.S. naturalized citizen
2Non-U.S. immigrant (permanent resident)
3Non-U.S. non-immigrant (temporary U.S. visa)
4Non-U.S., visa status unknown
UU.S. citizen, unspecified
BlankMissing or citizenship unknown

Respondents who indicated a U.S. birthplace, regardless of what they reported for citizenship status, were assigned code 0.

In 1999, code 4 (Non-U.S., visa status unknown) was introduced and data back through 1997 were back-coded. Respondents who designated a non-U.S. country for the country of citizenship item but did not respond to the citizenship status item were assigned code 4 for citizenship status. From 1997 to 2003, non-U.S.-born respondents who did not indicate their country of citizenship or citizenship status were assigned to code 4 if three out of four geographic variables—place of birth, place of high school, place of college entry, and postgraduation location—were non-U.S. locations. Beginning with the 2004 SED, the variable “place of baccalaureate institution” replaced “place of college entry” in the assignment of a citizenship code to respondents who did not indicate citizenship status.

For tabulations in this report, code 4 was combined with code 3—that is, counts of doctorate recipients in the temporary visa holder category include non-U.S. citizens with unknown visa status. This is consistent with coding procedures in previous data collections. However, the existence of code 4 allows the microdata user to exclude cases for which visa status is unknown, if desired. Prospective data users should note, however, that the number of cases in the code 4 group is not sufficient to warrant analysis as a separate citizenship category.

Non-U.S. citizens who did not report a country of citizenship but reported the same non-U.S. country for three out of four geographic variables—place of birth, place of high school, place of baccalaureate institution, and postgraduation location—were assigned that reported country as their country of citizenship.

Debt. Since 2001, respondents have been asked to indicate the amount of education-related debt they owe, with separate response categories for graduate and undergraduate education. To estimate overall debt, the midpoint of the chosen range for undergraduate and for graduate debt was selected and summed to yield a total debt amount. Where mean debt levels are presented in this report (i.e., tables 38 and 40), the individual values for debt are assigned as the midpoint of the chosen range for graduate and undergraduate debt. Doctorate recipients who chose the lowest debt category (No debt) were assigned a value of $0 for the computation of mean debt levels. Doctorate recipients who chose the uppermost category ($90,001 or more) were assigned a value of $95,000 for the computation of mean debt levels. All valid responses, including “No debt,” were included in the computation of all average debt figures in this report. See item A7 on the survey questionnaire for a complete listing of the debt ranges on which the midpoint figures were based.

Functional Limitations (previously, Disability). Beginning in 2012, item C12 (the “functional limitations” item) assesses both the presence and severity of functional limitations in each of several domains, which do not precisely overlap with the domains in prior surveys.

Eight new variable names and code frameworks were added, one of which captures responses to the disability items for respondents using pre-2012 SED questionnaire forms. The SED retains the disability variables used to capture data from the 2011 and older SED questionnaire forms for 2011 and older SED rounds.

Median computation. Since 1994, medians have been computed as outlined below. When months are included, they are converted to the number of days corresponding to first day of the month, factoring in leap years.

Median age. Months (of birth and doctorate award) are included in the calculation of median age whenever available. If birth month is missing in the calculation of median age, month value is assigned to the month the doctorate was received.

Time to degree from bachelor’s completion. Months are included in the calculation of total time to degree. If months are missing, month values are assigned to the number of days corresponding to the month of June, with a leap-year factor included (i.e., assignment to a value of 151.25).

Time to degree from graduate school entry. Months are included in the calculation of graduate school time to degree. If months are missing in the calculation of graduate school time to degree, month values are assigned to the modal value for doctorate recipients who provided month of graduate entry (i.e., assignment to a value of 243.25, which corresponds to the month of September). Reports published before 2004 reported a different time-to-degree measure, registered time to degree. Comparisons of graduate school time-to-degree data with pre-2004 registered time-to-degree data should be interpreted cautiously. For an explanation of registered time to degree, see the technical notes section of any Doctorate Recipients from United States Universities: Summary Report published before 2004.

Salary. Median salary is calculated from exact salary values when provided by the respondent. If a respondent selected a salary range instead of providing an exact salary value, exact salary values were imputed for median salary calculations by applying hot-deck imputation based on salary range and other relevant respondent characteristics. Only salary data from doctorate recipients reporting definite commitments for employment or for a postdoc position are included in median salary calculations.

Postdoctoral plans to stay in the United States. In 1997, the planned postdoctoral location of doctorate recipients began being coded in a new variable using Federal Information Processing Standards codes both for the United States and its territories and for countries.

Also in 1997, a dichotomous variable was created to index whether the planned postdoctoral location reported by the respondent was in the United States or in a foreign location, even if the respondent did not indicate a specific state or country.

Race and Hispanic ethnicity. Since 2001, respondents have been asked to first indicate whether or not they are Hispanic or Latino and then to check one or more racial group categories (i.e., American Indian or Alaska Native, Asian, Native Hawaiian or Other Pacific Islander, black or African American, or white).

In data tables, doctorate recipients who report Hispanic or Latino ethnicity, regardless of race, are counted as Hispanic or Latino, and as of 2013, those who did not answer the Hispanic or Latino question are counted as “Ethnicity not reported.” Respondents who indicate that they are not Hispanic or Latino and indicate a single race are reported in their respective racial groups, except for those indicating Native Hawaiian or Other Pacific Islander, who are included in “Other race or race not reported.” Beginning in 2007, doctorate recipients who indicate they are not Hispanic or Latino and indicate more than one race are reported in the group “More than one race,” which is relabeled to “Two or more races” in 2013 data tables.

Research doctoral degree. As doctoral degree programs change to meet the needs of students, the orientation of the degrees they award may change from research to professional, and vice versa. Survey staff review degree programs to ensure that the designation of research doctorate remains appropriate. As a result of degree reviews in the past two data collections, survey staff identified several research doctoral degrees that shifted to a professional orientation. The doctor of music (DM) and the doctor of industrial technology (DIT) were both dropped from the SED in 2008, and the graduates (approximately 40 to 60 per year) who earn these doctoral degrees are no longer included in the SED.

After a multiyear review of doctoral programs offering the EdD degree, most were determined to have a professional orientation and were dropped from the SED in 2010 and 2011, and graduates earning EdD degrees from those programs are no longer included in the SED. As a result, the proportion of EdD degrees among the total number of research doctorate recipients fell from 5.5% in 2009 to 1.3% in 2013. Table A-1 lists the doctoral degrees that were eligible for inclusion in the SED in 2013.


Basic annual salary. Annual salary to be earned from the doctorate recipient’s principal job in the next year, not including bonuses or additional compensation for summertime teaching or research.

Carnegie classification (institution categories). In this report, three types of doctorate-granting institutions identified in the figures and tabulations are defined according to the Carnegie Classification scheme as updated in 2010: very high research universities, high research universities, and doctoral research universities. Institutions are classified according to their aggregate and per-capita levels of research activity, using indicators of R&D expenditures and staffing (including postdoctoral appointees and other non-faculty research staff with doctorates) in S&E and non-S&E fields.

Definite plans to stay in the United States. A respondent is coded as having firm plans to stay in the United States if the reported postgraduation location was in the United States and the reported postgraduation plans were coded “definite.”

Definite postgraduation plans. The status of postgraduation plans is coded using the values from item B3 of the survey questionnaire, which indicate whether the doctorate recipient’s postgraduation plans were definite at the time the survey was completed.

Field of study.The SED has 317 fine fields of doctoral study, which are grouped into 35 major fields of study. The major field groupings are further aggregated into seven broad fields: life sciences, social sciences, physical sciences, engineering, education, humanities, and other fields. The levels of this variable were derived by grouping related fine fields of study from the field of study taxonomy used in the SED (table A-6). See the survey questionnaire for a full listing of the fine fields of study in 2013.

Doctorate recipients indicate their fields of specialty. Their choices may differ from departmental names. Field groupings may differ from those in other reports published by federal sponsors of the SED. The “general” field categories (e.g., “chemistry, general”) include individuals who either received the doctorate in the general subject area or who did not indicate a particular specialty field. The “other” field categories (e.g., “chemistry, other”) include individuals whose specified doctoral discipline was not among the specialty fields listed.

Median age at doctorate. One-half of the respondents received the doctorate at or before this age. A recipient’s age is obtained by subtracting the month and year of birth from the month and year of doctorate.

Percentage with master’s. This variable is the percentage of doctorate recipients in a field who received a master’s degree in any field before earning the doctorate.

Research doctorate. A research doctoral degree is oriented toward preparing students to make original intellectual contributions in a field of study and is not primarily intended for the practice of a profession. Research doctorates require the completion of a dissertation or equivalent project.

Time to doctorate. The SED measures the time it takes to complete a doctoral degree in two ways: (1) the time elapsed from completion of the baccalaureate to completion of the doctorate (total time to degree), and (2) the time elapsed from the start of any graduate school program to completion of the doctorate (graduate school time to degree). Time-to-doctorate measures herein are reported as medians.

Total time to degree. This variable is the total elapsed time between the baccalaureate and the doctorate, including time not enrolled in school. It can be computed only for individuals whose baccalaureate year is known. Baccalaureate year is often obtained from commencement programs or doctorate institutions when not reported by the recipient.

Graduate school time to degree. This variable is the elapsed time from the initiation of graduate study, in any program or capacity at any university, and the award of the doctorate. This variable can be computed only for individuals who provided the year they started graduate school. If an individual did not respond to question A11, which asks for the month and year of first entry into any graduate school, and did not report a graduate school degree program in question A9, which asks for additional postsecondary degrees, then values for graduate school month and year of entry are imputed from the month and year of entry into the most recent master’s degree program (A8) or, if that is missing, the month and year of entry into the doctoral degree program (A8). Months are included in the computation.

U.S. regions of employment. This variable is used to classify the location of U.S. employment after award of the doctorate.

New EnglandConnecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont
Middle AtlanticNew Jersey, New York, Pennsylvania
East North CentralIllinois, Indiana, Michigan, Ohio, Wisconsin
West North CentralIowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, South Dakota
South AtlanticDelaware, District of Columbia, Florida, Georgia, Maryland, North Carolina, South Carolina, Virginia, West Virginia
East South CentralAlabama, Kentucky, Mississippi, Tennessee
West South CentralArkansas, Louisiana, Oklahoma, Texas
MountainArizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, Wyoming
Pacific and InsularAlaska, California, Hawaii, Oregon, Washington, American Samoa, Guam, Puerto Rico, Trust Territories, Virgin Islands

Appendix Tables

TableSummary Report Data: 2013ExcelPDF
A-1Types of research doctoral degrees recognized by the Survey of Earned Doctorates: 2013 View Excel View PDF
A-2Research degrees included in the Survey of Earned Doctorates: 2009–13 View Excel View PDF
A-3Survey response rates: 1976–2013 View Excel View PDF
A-4Item response rates: 2003–13 View Excel View PDF
A-5Aggregated fields and their constituent fine fields: 2013 View Excel View PDF
A-6Aggregations used to determine major fields of study: 2013 View Excel View PDF


[1] U.S. Department of Education. 1996. Mapping the World of Education: The Comparative Database System (CDS). Vol. 1, 2, and 3. Arlington, VA: National Science Foundation. Available at http://www.nsf.gov/statistics/mapping/. 2006. Europa World of Learning. London: Routledge-Taylor & Francis Group. Serial and online database available at http://www.worldoflearning.com/.