MnSCU –
2002 Salary Equity Analysis
March, 2003
Prepared
by:
Thomas McMullen
Senior Consultant
Hay Group
Consultant
Hay Group
Malcolm M. Dow
Professor Emeritus
Northwestern University
Table of Contents
I. Executive Summary............................................................................................................... 1
II. Faculty Salary Equity Analysis................................................................................................ 2
A. Brief Description of Average Faculty Salary Differentials by Gender and Ethnicity................... 2
1. Faculty Salary By Gender.................................................................................................. 2
2. Faculty Salary By Gender and Rank.................................................................................... 2
3. Faculty Salary By Gender and Ethnicity............................................................................... 3
B. Promotion to Academic Rank................................................................................................ 3
C. Controlling Salary For Structural Factors: Multiple Regression Analysis................................... 6
2.... Natural Log of Salary Regression Model........................................................................ 10
D. Total Population Model Without Discipline Variables............................................................ 11
E. Individual-level Salary Differences: Regression Residuals...................................................... 12
F. Summary............................................................................................................................. 14
This statistical analysis of the Metropolitan State faculty salary data used the Multiple Regression model to predict salaries based on a number of factors known to affect pay. Variables coding for gender and minority status were included in the analyses. No faculty performance measures were included.
The analyses indicate that White and Under-represented females, and African American and Asian male faculty earn less on average than similarly situated White male faculty. None of the corresponding regression coefficients were statistically significant, however.
The regression without the rank variable indicated some masking of salary bias in three protected classes. However, the extent of masking was not sufficient to indicate statistically significant salary deficits for the corresponding protected classes.
No evidence of salary compression was found.
A Multinomial Logistic Regression of the Academic Rank variable indicated that none of the odds of promotion to higher Rank for White males versus any protected class were statistically significantly different. However, the Total Population Model without the Rank variable suggests some masking of bias in average salary due to the rank variable.
The first three tables reported in this section are intended to provide a very brief indication of the variation in average 2002 yearly salaries across ethnic and gender groupings of Metropolitan State faculty. Explaining as much of this variation in salary as possible, using additional background factors such as academic rank and length of service, is the focus of this report.
Table 1 shows a $4,085 shortfall in average annual salary for female relative to male faculty. Several factors that account for much of this difference will be discussed below.
Table 1. Average 2002 Salary by Gender
|
M/F |
Mean |
N |
Std. Dev |
|
F |
52909 |
48 |
9234 |
|
M |
56994 |
55 |
10324 |
|
Total |
55091 |
103 |
9996 |
One major factor that affects faculty salary differences is Academic Rank. Table 2 reports average annual salaries broken out by Gender and Rank. At the Assistant Professor Females earn on average $3,422 less than males. At the Associate Professor and Professor ranks, male salaries are on average $315 and $6,162, respectively, above the female averages.
Table 2. Average 2002 Salary by Rank and Gender.
|
rank |
M/F |
Mean |
N |
Std. Dev |
|
professor |
F |
63657 |
10 |
7672 |
|
M |
69819 |
13 |
8338 |
|
|
|
|
|
|
|
|
associate professor |
F |
56384 |
15 |
6833 |
|
M |
56699 |
21 |
6367 |
|
|
|
|
|
|
|
|
assistant professor |
F |
45970 |
23 |
4158 |
|
M |
49392 |
20 |
6255 |
|
|
|
|
|
|
|
|
instructor |
F |
* |
0 |
|
|
|
M |
* |
1 |
|
Table 3 reports average salary differences broken out by a combination
of Gender and Ethnicity. Small numbers
of protected classes were grouped together.
Comparing the average salary for White males to the other averages
reveals that for all other categories earn less on average than the average for
White males. There are 103 faculty
members in the total population.
Table 3. Average 2002 Salary by Ethnicity-Gender.
|
ethnicity-gender |
Mean |
N |
Std. Dev |
|
white female |
53296 |
37 |
10081 |
|
african amer
female |
* |
4 |
|
|
asian female |
* |
3 |
|
|
hispanic female |
* |
4 |
|
|
white male |
58518 |
40 |
11327 |
|
african amer male |
51974 |
5 |
4225 |
|
asian male |
54881 |
5 |
5997 |
|
hispanic male |
* |
3 |
|
|
native amer male |
* |
2 |
|
*
Data are omitted if less than five faculty members within a grouping.
We note that this analysis uses current data patterns within campus to assess odds ratios for promotion. This analysis did NOT examine actual rates of promotion acceptance and rejection within a campus, as this data were not available for analysis. That is, we analyzed only the current distribution of faculty within ranks, broken out by ethnicity-gender. For example, at Metropolitan there are 14 White male Assistant Professors and 14 White male Associate Professors, with corresponding odds of 14/14 (=1.0) of moving from Assistant to Associate rank. For White females there are 18 Assistants and 11 Associates, with corresponding odds of 11/18 (=0.611) of being Associates. The “odds ratio” of White females to White males getting promoted from Assistant to Associate is then (0.611/1.0) = 0.611; that is, White female odds of moving to Associate are only 61.1% of the White male odds. The multinomial Logistic regression model adjusts these odds ratios to take into account the effects of other variables that might factor into promotion decisions, such as highest degree, previous experience, length of service, etc. When these control variables were added to the Multinomial regression model, the odds ratio improved slightly, from 0.611 to 0.638 (see Table 4 below).
Table 4 shows the estimated odds ratios of promotion from Assistant Professor to Associate Professor and from Associate Professor to Professor obtained using the Multinomial Logistic Regression model. The odds ratios were calculated after controlling for Highest Degree, Years of Prior Experience, and Total MnSCU years. Odds ratios greater than 1.0 indicate a correspondingly greater likelihood for individuals in the indicated category in obtaining promotion to the next category. Conversely, odds less than 1.0 indicate less likelihood.
Three to five minority dummy variables – Under-represented
females, White females, Asian males, African American males, and
Under-represented males – were included in predicting odds of promotion to
higher rank. Because categorical modeling cannot handle groupings with very low
frequency for combinations of attributes (e.g. African American + female +
associate professor), some protected classes are combined.
|
Table 4. Odds
of Promotion to Higher Rank by Gender and Ethnicity |
|||
|
|
|
|
|
|
|
|
Sig. |
Exp(b)=Odds Ratio |
|
assistant to
associate |
White female to
White male |
0.487 |
0.638 |
|
Under-rep female to
White male |
0.677 |
0.665 |
|
|
|
Under-rep male to
White male |
0.755 |
1.391 |
|
|
Afr Amer male
to White male |
0.790 |
1.390 |
|
|
Asian male to White
male |
0.869 |
0.831 |
|
|
|
|
|
|
associate to
professor |
White female to
White Male |
0.372 |
1.713 |
|
Under-rep female to
White male |
0.604 |
1.638 |
|
|
|
Asian male to White
male |
0.806 |
1.310 |
Table 4 shows the odds of promotion and associated statistical significance levels for protected classes as compared to White males. There is no analysis for promotion from Instructor to Assistant Professor since there are no instructors (one instructor was recoded as assistant prof.) Under-represented females, Asian males, and White females have lower odds of promotion from Assistant to Associate than the corresponding male categories, although no coefficient is statistically significant. The Under-represented and African American male coefficients are greater than one but are not statistically significant. At the Associate to Professor promotion, all protected groups have better odds than the White male categories, although no coefficient is statistically significant.
In general, at least one of the Prior experience, Total MNSCU years, or Years since Highest Degree control variables was highly significant in each equation examined here.
Since none of the promotion odds coefficients for protected
classes are statistically significant, there is no statistically significant
evidence from this analysis to indicate that the Academic Rank variable is
“tainted.” This question will be
addressed again below in the Total Population without the Rank variable
section.
1. Total Population
Salary Analysis
Table 5 reports the estimated regression equation and auxiliary statistics for the Total Population Analysis (N=103). In this model, the dependent variable is 2002 Annual Salary, and the predictor variables are all of the structural variables plus a set of dummy variables corresponding to ethnic minority and gender status. The numbers of individuals within the Hispanic male (N=3) and Native American male (N=2) classes were collapsed into Under-represented male (N=5) category. Similarly, the African American (N=4), Asian (N=3), and African American females (N=4) were collapsed into an Under-represented female (N=11) category. There are sufficient White females (N=37) for a separate variable. The reference category is thus White males (N=40).
The first column of Table 5 shows the labels of each of the variables entered into the regression model. The first term (constant) can be ignored. Each of the other terms in the first column corresponds to either a “structural” variable or one of the ethnicity-gender variables.
The second column in Table 5 shows the “unstandardized coefficient” B associated with each variable, which indicates the average amount by which each faculty member’s salary increases (or decreases) for a one unit change in the corresponding variable, all of the other variables in the equation being held constant. In the case of a dummy variable, the one unit change is from the omitted reference category (coded as 0) to the corresponding category (coded as 1). So, for example, the coefficient for White females in the second column indicates that an individual moving from the “White male” category (coded as 0) to the “White female” category (coded as 1) would be expected to have an increase (positive coefficient) in annual salary of $615, all other variables in the regression model being equal. For continuous variables, such as Prior Years of Experience, the corresponding unstandardized coefficient ($33) indicates how much each additional unit (here, a year) is worth, on average.
Table 5. Total Population Model with Ethnicity-Gender Variables.
|
|
|||||||
|
|
Unstandardized |
Standardized |
t |
Sig. |
Collinearity |
||
|
B |
Std. Error |
Beta |
Tolerance |
VIF |
|||
|
(Constant) |
54295 |
2859 |
|
18.992 |
0.000 |
|
|
|
|
|
|
|
|
|
|
|
|
ARTFI |
|||||||