A recent study by sociologists at Indiana University and Cornell University offers a new explanation for the persistent wage gap. Sociology professors Youngjoo Cha and Kim A. Weeden looked at data from the Census Bureau and Bureau of Labor Statistics' Current Population Survey over the last 30 years.Their study showed that men were more likely to work extra hours and were compensated monetarily for that time. Weeden and Cha suggest that the "overwork effect" is significant enough to neutralize other wage increasing factors that have changed over the years, such as more women earning college degrees than men. Cha and Weeden also explain that the reason women may be less likely to take on extra hours at work is because they are still tasked with the majority of housework and child care responsibilites. Read their study here.