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................................... 5
2.... Natural Log of Salary Regression Model.......................................................................... 8
D. Total Population Model Without Discipline Variables............................................................ 10
E. Individual-level Salary Differences: Regression Residuals...................................................... 12
F. Summary............................................................................................................................. 13
This statistical analysis of the Bemidji 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 the Under-represented minorities category earn on average $1,376 less than similarly situated White male faculty, which corresponds to an approximately 2.3% average deficit. These coefficients are not statistically significant.
There is no evidence from the regression analyses of salary compression for faculty with many years in current rank.
A Multinomial Logistic Regression of the Academic Rank variable indicated that the odds of promotion to higher Rank for White males versus the three protected classes were not statistically significantly different. This finding was confirmed with the results from the Total Population Model without the Rank variable, which showed no salary bias due to the Rank variable. Thus, no “taint” in Rank was uncovered by these analyses.
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 Bemidji 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 $5,729 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 |
49815 |
84 |
10433 |
|
M |
55544 |
125 |
11801 |
|
Total |
53241 |
209 |
11592 |
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 Instructor, Assistant Professor, Associate Professor and Professor ranks, male salaries are on average $5, $764, $1,422, and $2,973 respectively, above the female averages.
Table 2. Average 2002 Salary by Gender and Rank
|
rank |
M/F |
Mean |
N |
Std. Dev |
|
professor |
F |
62271 |
24 |
6279 |
|
M |
65244 |
57 |
8467 |
|
|
|
|
|
|
|
|
associate professor |
F |
44916 |
36 |
4558 |
|
M |
46338 |
32 |
5334 |
|
|
|
|
|
|
|
|
assistant professor |
F |
34253 |
10 |
2498 |
|
M |
35017 |
8 |
2684 |
|
|
|
|
|
|
|
|
instructor |
F |
52177 |
14 |
4446 |
|
M |
52182 |
28 |
4546 |
|
|
|
|
|
|
Table 3 reports average salary differences broken out by a combination of Gender and Ethnicity. Again, this table shows substantial salary differences in average salaries across these groupings. Comparing the average salary for White males to the other averages reveals that White females earn less on average than the average for White males. However, the Asian and Hispanic males earn more on average.
Table 3. Average 2002 Salary by Ethnicity-Gender
|
ethnicity-gender |
Mean |
N |
Std. Dev |
|
White female |
49810 |
82 |
10520 |
|
African amer female |
* |
1 |
|
|
Hispanic female |
* |
1 |
|
|
White male |
55574 |
114 |
11773 |
|
Asian male |
* |
4 |
|
|
Native amer male |
55690 |
5 |
17240 |
|
unknown |
* |
2 |
|
|
Total |
53241 |
209 |
11592 |
* Data are
omitted if less than five faculty members within a grouping.
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 Length of Service. 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.
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 Bemidji in 2002 there were 28 White male Assistant
Professors and 27 White male Associate Professors, with corresponding odds of
27/28 (= 0.964) of moving from Assistant to Associate rank. For White females there are 35 Assistants and
13 Associates, with corresponding odds of 13/35 (=0.371) of being Associates. The “odds ratio” of White females to White males
getting promoted from Assistant to Associate is then (0.371/0.964) = 0.385;
that is, White female odds of moving to Associate are only 38.5% 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 additional variables were entered
into the Multinomial Regression model below, for example, the odds ratio for
White females improved slightly, to 0.541 from 0.385.)
Two minority dummy variables –White females and All Minorities – 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), all minority groupings had to be combined as separate category.
|
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 |
0.180 |
0.541 |
|
All minorities to
White male |
0.295 |
0.249 |
|
|
|
|
|
|
|
associate to
professor |
White female to
White male |
0.561 |
1.347 |
|
All minorities to White
male |
0.806 |
1.376 |
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 is “complete separation” on the Highest Degree variable. That is, holding a doctorate completely predicts this promotion step in this data.
White females and All minorities have lower odds of promotion from Assistant to Associate than the corresponding White category, although neither of these coefficients is statistically significant. Associate to Professor shows White females and Under-represented males having better odds than the White male category, although neither coefficient is statistically significant.
In general, at least two of the control variables of Doctorate, Total MnSCU years, and Years since Highest Degree were highly significant in the equations 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 issue is examined
further below in the regression analysis that omits the Rank variable.
1. Total Population
Salary Analysis – with and without the Academic Rank variable
Table 5 reports the estimated regression equation and auxiliary statistics for the Total Population Analysis (N=209). 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. Since there are sufficient numbers of Native American males (N=5) to conduct an analyses using this variable, this category was entered into the model as a separate variable. The remaining African American female, Hispanic female, and 4 Asian Pacific Island males were collapsed into an Under-represented minorities category (N=6). There are sufficient White females (N=82) for a separate variable. The two (2) Unknown faculty were entered as a separate dummy variable simply to ensure that the reference category consisted of only White males.
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 $247, all other variables in the regression model being equal. For continuous variables, such as Years since Highest Degree, the corresponding unstandardized coefficient ($64) 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) |
57168 |
1205 |
|
47.430 |
0.000 |
|
|
|
|
|
|
|
|
|
|
|
|
ACCTG |
8295 |
1848 |
0.120 |
4.488 |
0.000 |
0.644 |
1.553 |
|
ARTFI |
1675 |
1847 |
0.031 |
0.907 |
0.366 |
0.395 |
2.533 |
|
BIOLO |
1011 |
1434 |
0.020 |
0.705 |
0.482 |
0.551 |
1.814 |
|
BUSAD |
4057 |
1666 |
0.067 |
2.435 |
0.016 |
0.600 |
1.666 |
|
CHEMS |
853 |
1627 |
|||||