Absence of conflict of interest.
Citation
Highlights
-
The study's objective was to examine the impact of the Illinois Equal Pay Act of 2003 on the difference in earnings and employment outcomes for men and women.
-
The authors used a difference-in-difference design to compare changes in outcomes before and after the implementation of the Illinois Equal Pay Act relative to a comparison scenario. Using statistical models and data from the Census Bureau's Current Population Survey (CPS), the authors estimated the law’s impact on employment and earnings outcomes for men and women.
-
The study found a significant relationship between the Illinois Equal Pay Act of 2003 and a reduction in the gender wage gap in Illinois compared to other states. However, it also found a significant relationship between the legislation and a reduction in the number of hours that women worked.
-
This study receives a low evidence rating. This means we are not confident that the estimated effects are attributable to the Illinois Equal Pay Act of 2003; other factors are likely to have contributed.
Intervention Examined
Illinois Equal Pay Act of 2003
Features of the Intervention
The federal Equal Pay Act was passed in 1963, prohibiting pay discrimination based on gender for equal or comparable work. It was not expected to have any real impact at the time, but it set the stage for later legislation that would prohibit pay discrimination based on gender. The Illinois Equal Pay Act of 2003, which took effect in 2004, forbids pay discrimination based on gender. The basic enforcement mechanism is complaint filing through the Illinois Department of Labor (IDOL). Under the law, if employers are found to have underpaid an employee based on their gender, they must deliver the entire amount that was underpaid, plus interest and any reasonable attorney's fees associated with the process. Amendments were passed in 2009 and 2014 to strengthen the law.
Features of the Study
The authors used a difference-in-difference design to examine the impact of the Illinois Equal Pay Act of 2003. The main data source was the Census Bureau's Current Population Survey (CPS) which provided information such as age, gender, employment status, wage, and hours worked. The authors used a random sample of approximately 200,000 American households per year from 2000-2016. Within this sample, only employed individuals between the ages of 25 and 55 were selected for inclusion in the study. Employees who lived in Illinois (the treatment group) were protected under the equal pay law after 2003. The authors created a comparison group from 46 states, excluding Alabama, California, Maine, and New Jersey due to differences in gross domestic product, culture, or having passed similar legislation to Illinois' Equal Pay Act. The authors used statistical models with fixed effects for state and year to compare gender differences in median hourly wage (gender wage gap) and the number of hours worked (female workshare) before and after the law.
Findings
Earnings and compensation
-
The study found a significant relationship between the Illinois Equal Pay Act of 2003 and a reduction in the gender wage gap in 2005 and 2006, but not for 2004. The same pattern was found for the 2009 Amendment (significant relationship in 2010 and 2011, but not 2012).
-
The study also found that there was a significant relationship between the 2013 Amendment and the gender wage gap in 2015, but not in 2014 or 2016.
Employment
-
The study found a significant relationship between the Illinois Equal Pay Act of 2003 and a reduction in the female workshare in 2005 and 2006, but not for 2004.
-
The study found that for the 2009 Amendment, there was a significant relationship between the law and a reduction the female workshare in 2012, but not in 2010 or 2011.
-
The study also found that there was a significant relationship between the 2013 Amendment and a reduction the female workshare in all years.
Considerations for Interpreting the Findings
The authors created a synthetic comparison group using data from other US states. While they excluded some states for having similar legislation or demographic differences, only four were excluded. However, multiple states passed Equal Pay legislation between 2000-2016. Because the analysis considered a policy operating in only one state, it is impossible to disentangle the effect of the Illinois Equal Pay Act of 2003 from the effect of the state itself; this is known as a confounding factor. For instance, there could have been other changes occurring at the state level at the same time that could also have affected the outcomes of interest. We cannot attribute the estimated effects with confidence to the Illinois Equal Pay Act of 2003, and not to other factors. Therefore, the study is not eligible for a moderate causal evidence rating, the highest rating available for nonexperimental designs.
Causal Evidence Rating
The quality of causal evidence presented in this report is low because the program was implemented in only one state presenting a confounding factor. This means we are not confident that the estimated effects are attributable to the Illinois Equal Pay Act of 2003; other factors are likely to have contributed.