APPENDIX A
1991 SURVEY CHANGES
In 1991, a number of methodological changes were made to the Survey of Humanities Doctorates. These changes distinguish 1991 data from those collected in earlier years. The changes are described below.
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Sampling Frame. The 1991 sampling frame was redefined to include only doctorates who were 75 years of age or younger in September 1991. In prior surveys, the frame had excluded individuals on the basis of years since the award of their degree, not on the basis of age. Under that definition, individuals who had earned their degrees more than 42 years prior to the survey year were excluded (or at about age 72). This change was made to accommodate growing interest in retirement issues.
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Sample Design and Sample Size. Because of budgetary constraints, the initial 1991 sample was cut in half--from 17,716 to 8,894 sample cases. At the same time, it was restratified into fewer sampling cells and greater homogeneity in sampling rates across strata was introduced. These changes were made to reflect current analytic interests.
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Response Rates. The resources saved as a result of the sample size reduction were redirected toward increasing the response rate, which had fallen to about 55 percent in 1989. The approach was two-pronged. First, the mail survey was made more productive through (a) extensive efforts to locate and update addresses for individuals in the sample, (b) reformatting of the survey questionnaire (the content did not change), and (c) the use of personalized mailing techniques. Second, a sample of about 60 percent of the nonrespondents was followed up by telephone. As a result of these efforts, the overall response rate to the 1991 survey increased to 78 percent (unweighted). Most likely, this reduced the effects of nonresponse bias in the 1991 survey estimates.7
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Reference Period. Due to the Change in the schedule for fielding the survey (traditionally, mailing had commenced in March or April of the survey year), the reference date for survey items was moved from February to September. Thus, 31 months elapsed between the 1989 and 1991 surveys, compared with 24 months between previous surveys.
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A study conducted on a sample of science and engineering doctorates who were nonrespondents to the 1989 SDR showed bias due to the low response rate in several variables, including location, type of employer, primary work activity, and tenure status. The findings were that the size of the U.S. population of doctorates was being overestimated, as were the numbers of those employed in the academic sector and the numbers of those teaching. To the extent that these biases existed in estimates of the humanities population, they should be minimized by the higher response rate in 1991. For additional information, see S. Mitchell and D. Pasquini, Nonresponse Bias in the 1989 Survey of Doctorate Recipients: An Exploratory Study, Office of Scientific and Engineering Personnel, National Research Council, Washington, D.C., 1991.
TABLE 22 Publications of Humanities Ph.D.s Employed in Academe, by Field of Doctorate and Tenure Status, 1991 (in percent)
Number of Publications |
||||||
Field of Doctorate and Tenure Status |
Total* (No.) |
None |
1-2 |
3-5 |
More Than 5 |
Mean |
Total |
60,000 |
31.2 |
21.7 |
22.7 |
24.4 |
4.2 |
Field of Doctorate |
||||||
American History |
3,800 |
20.4 |
20.1 |
25.4 |
34.1 |
6.1 |
Other History |
9,200 |
26.3 |
19.5 |
24.7 |
29.4 |
5.0 |
Art History |
1,900 |
15.4 |
32.2 |
29.0 |
23.4 |
4.0 |
Music |
5,000 |
61.0 |
16.4 |
10.5 |
12.1 |
2.1 |
Speech/Theater |
3,100 |
43.3 |
20.1 |
18.1 |
18.5 |
3.6 |
Philosophy |
4,900 |
26.6 |
22.7 |
23.6 |
27.1 |
4.2 |
English and Amer Lang/Lit |
17,000 |
33.2 |
24.9 |
21.8 |
20.1 |
3.8 |
Classical Lang/Lit |
1,300 |
29.7 |
20.5 |
28.1 |
21.8 |
3.5 |
Modern Lang/Lit |
9,900 |
26.8 |
20.3 |
24.8 |
28.1 |
4.6 |
Other Humanities |
3,900 |
21.5 |
19.9 |
27.6 |
30.9 |
4.9 |
Tenure Status† |
||||||
Tenured |
37,300 |
28.7 |
21.0 |
23.4 |
26.9 |
4.6 |
Not Tenured |
20,700 |
35.3 |
22.7 |
21.7 |
20.2 |
3.6 |
Tenure Track |
9,600 |
21.0 |
23.4 |
29.6 |
26.0 |
4.3 |
Nontenure Track |
4,200 |
40.3 |
24.8 |
20.4 |
14.5 |
3.3 |
Tenure Not Applicable |
6,900 |
52.3 |
20.4 |
11.6 |
15.7 |
2.7 |
*Totals in this table are equal to the number answering the question on publications, not the total sample, and may therefore disagree with totals shown elsewhere in the report. †Subcategories do not add to total because no reports are not shown. |