Examining the Gender Pay Gap at Purdue University
Earlier this year, the topic of the gender pay gap prominently resurfaced due to the initiation of 2020 presidential campaigns. While watching the first Democratic debate three weeks ago, I developed an interest in exploring whether such a pay gap even existed between males and females. As a data science major at Purdue, I thought a good place to start would be at my own university. My goal was to determine if there is a statistically significant difference in wages between male and female staff members.
I started by emailing Purdue Public Records for the 2018 salary book. Within two days, they sent me back an excel spreadsheet of almost 17,000 rows containing employee salaries from over 125 cities in Indiana. For the purposes of my study, I focused on West Lafayette, the location of Purdue’s main campus. Using excel, I organized the data by removing the employees who do not work in West Lafayette. I then loaded the data into RStudio where I could calculate some descriptive statistics.
The statistics
At first glance of the statistics, the mean male salary is about $24,000 dollars higher than the mean female salary. However, it should be noted that the highest male salary is $4,220,755, an outlier which pulls the mean male salary up, while the highest female salary is merely $704,660. Furthermore, the median male salary is almost $12,000 dollars higher than the median female salary. While the mean and median salaries for males are higher than those of females’ salaries, I decided to conduct further analysis to identify if this gap is statistically significant.
Analysis
In order to determine if this pay gap was statistically significant, I used a hypothesis test. The sample() function in R allowed me to sample 500 salaries each from the male and female salary data. Since I knew the standard deviations of the data sets, I used a two sample z-test (below) to evaluate the difference between the means in both of these sample groups.
- Null Hypothesis: Male and female sample means are equal
- Alternative Hypothesis: Male sample mean is greater than the female sample mean
- Alpha value: 0.05
After conducting the hypothesis test, the resulting p-value was significantly lower than my alpha value of 0.05. Therefore, I rejected the null hypothesis and I am 95% confident that the mean male salary is greater than the mean female salary. This test shows that the difference of the means is statistically significant. Furthermore, because the appropriate sampling conditions were met, I can extrapolate this conclusion to the populations and say that the difference of salaries between male and female staff members was statistically significant in the 2018 calendar year.
To further affirm my findings, I calculated the 95% confidence intervals for both male and female salaries (below) using the same null and alternative hypotheses.
As you can see from the results, the 95% confidence interval for males from this sample is $67,769.29 — $78,332.01. For females, it is $45,938.07 — $51,873.74. I am 95% confident that the true male and female salary means lies within their respective confidence intervals. This is noteworthy because these intervals do not overlap, implying that the difference between the means is significant.
So, why is this the case? What are the root causes for the gender gap at Purdue?
Athletics
A major contributor to the gender gap at universities is with athletics. The athletics department at many NCAA Division I institutions is a driving force for revenue. Two of the major college sports that consistently generate the most revenue are football and men’s basketball. In fact, a Business Insider article from 2017 found that college football generated an average of $32 million dollars for their respective universities. To quote the article, “At the University of Texas, the school with the most revenue from athletics ($182 million), 70% comes from football.” Men’s basketball is a far second place at a little over $8 million dollars, much of this coming from the NCAA March Madness tournament.
Aside from the fact that these sports generate a lot of revenue for universities, male staff members tend to dominate athletics departments. At Purdue for instance, 23 of the top 24 highest paid staff members in the athletics department are male.
Moreover, Purdue allocates the most staff salary on the athletics department at $32,191,594 (4.2% of total staff salary spending). So clearly, the athletics department provides a major skew where it raises the mean male salary. With Purdue spending this much money on male staff members in the athletics department, it merits a further question: Why don’t universities pay female coaches just as much?
Professorship
Another major contributor to the gender gap at universities has been the male-to-female ratio in professorship. In academia, the positions are ranked as follows: professor, associate professor, assistant professor, instructor, and lecturer. As a person climbs up the ranks, their pay hikes up as well. However, the process for a tenure-track assistant professor to achieve tenure is rather long. On average, it takes six years for an assistant professor to get promoted to a tenured associate professor position.
In an article from the National Center of Educational Statistics, it finds that there are more female instructors and lecturers over males. However, there are more male professors than there are female professors. In addition, a study from the Teachers Insurance and Annuity Association (TIAA) Institute found that even though universities are currently hiring more female assistant professors, most are not on tenure-track. In turn, an income disparity is created where male faculty members end up making more than female faculty members.
For example, the Electrical Engineering, Management, and Mechanical Engineering departments at Purdue are the top three academic departments in terms of staff salary. Here are the number and percentage of female faculty members in each department mentioned:
- Electrical Engineering: 27/134 = 20.1 %
- Management: 19/74 = 25.7 %
- Mechanical Engineering: 18/110 = 16.4 %
This shows that there are not enough females in academia. In order for more females to become tenured professors, Purdue and other universities need to step up and hire more tenure-track female assistant professors while also promoting more females to tenured professorship. If this can be accomplished, then it will create a diverse environment which will lead to a thriving academic community.
Conclusion
At Purdue University, the gender pay gap exists. It is clear that loads of money are poured into the athletics department where male athletes and coaches receive more attention than females since they generate a lot of revenue. Additionally, academic departments are filled with a massive gender disparity at the tenured professorship level.
As a matter of fact, Purdue has a high male-to-female ratio at 1.04, but this isn’t indicative of the entire population. At the departments where the most money is spent, at the top of the ladder, the male-to-female ratio is 3:1, 4:1, or sometimes even higher. In order to have a truer representation of the “real world”, more females need to be hired into high-ranked roles and receive appropriate pay equivalent to their male peers. Each year, the admissions office at Purdue admits a diverse and well-rounded class full of bright individuals. Every Purdue department should follow suit and introduce a diverse and well-rounded staff while working towards no gender pay gap at all.
Special thanks to Vijay Bharadwaj for helping edit this piece
