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More on Biostatistics

1 January 2010 3,799 views No Comment
Keith Crank, ASA Research and Graduate Education Manager

    In the article “Salary Survey of Biostatistics and Other Biomedical Statistics Departments,” I provide tabulations of salary information from the survey the ASA conducted last fall. The tables are for academic biostatisticians in both faculty and nonfaculty positions. The only surprising item (at least to me) is the big jump in salaries for new assistant professors. I believe this jump may be due more to the places that reported new assistant professors in the survey than to a big increase in what departments are willing (or able) to pay. However, it is a good sign for our profession that jobs with good pay are available.

    This year, for the first time, we asked for gender information along with the salaries. I will suggest a story for the gender information provided in Table 2. (This is by no means the only explanation for these numbers, but it is one that seems reasonable to me.) As background, I refer you to a recent report of the National Research Council (NRC) titled “Gender Differences at Critical Transitions in the Careers of Science, Engineering, and Mathematics Faculty.”

    Women accounted for approximately 55% of the PhDs in biostatistics over the past three years. Yet, only 47% of the people in the assistant professor category with one to three years in rank are women. The NRC report suggests this is not necessarily due to biases in the hiring practices of biostatistics departments. Their data indicate that women do not apply for tenure-track positions at the same rate as men. (See Chapter 3.)

    The NRC report also discusses tenure and promotion. But, an important issue in this area is attrition before faculty reach those milestones. The NRC report does not address attrition directly, because the authors did not obtain data allowing them to do so. But, the data for biostatistics faculty suggests attrition of women may occur at a higher rate than for men in the assistant professor ranks. While 47% of the assistant professors with one to three years in rank are women, only 38% of the assistant professors with four or more years in rank are women. (Although it is possible women are granted tenure earlier than men, this is not supported by the data in the table. If this were the case, one would expect the percentage of women in the associate professor, zero to two years in rank, to be between 38% and 47%, but women only account for 37% of those reported in this category.)

    Men and women appear to be getting tenure at comparable rates. The percentages of women in the assistant professor, four or more years in rank, and the associate professor, zero to two years in rank, are similar at 38% and 37%, respectively. Again, this is consistent with the NRC report, which indicates that when tenure decisions are being made, women are granted tenure at rates that are at least as high as men.

    For promotion from associate to full professor, the NRC report indicates women and men are promoted at comparable rates. However, this does not appear to be the case for biostatistics faculty. The percentage of women in the associate professor, three or more years in rank, is 41%, while the comparable percentage for full professors, zero to six years in rank, is only 30%. In addition, the percentage of women is higher for associate professors with three or more years in rank than it is for associate professors with zero to two years in rank. This suggests women in biostatistics departments are more likely than men to remain as an associate professor, rather than being promoted to full professor.

    This does not necessarily mean biostatistics departments are biased against their female associate professors. In fact, the higher salaries for women associate professors with three or more years in rank would suggest otherwise. An alternative explanation is that money, a major incentive for promotion to full professor, is less of an issue for biostatistics faculty than it is for faculty in other disciplines. In the February 2009 issue of Amstat News, I showed graphs of salaries for both statistics and biostatistics faculty. For associate professors, salaries of statistics faculty decreased with years in rank, while salaries of biostatistics faculty increased with years in rank. This suggests to me that female biostatistics faculty may not feel the promotion to full professor is that important, given the other demands on their time.

    The scenario above is only one of many possible explanations for the information in the biostatistics salary table. While preparing the table, I found it interesting how consistent it seemed to be with the results of the NRC report. And I don’t want to say that biases don’t exist, only that other explanations also may be plausible.

    To contact me, send an email to keith@amstat.org. Questions or comments about this article, as well as suggestions for future articles, are always welcome.

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