"[Most] wage differences can be explained by 'observable differences in the attributes of men and women,' including, among many, the fact that a greater percentage of women than men take leave for childbirth and child care, which tends to lead to lower wages. Also, women may place more value on 'family-friendly' workplace policies and prefer non-wage compensation, such as health insurance or flexibility.

"The statistical analysis, which included these and other variables, produced an adjusted gender wage gap between 4.8 percent and 7.1 percent. The gap shrinks to almost nothing when men and women of equal backgrounds and tenure are compared, according to another study of young, childless men and women."

In 2009 the Labor Department commissioned an analysis of more than 50 peer-reviewed wage-gap papers and concluded that the aggregate wage gap "may be almost entirely the result of the individual choices being made by both male and female workers." American Enterprise Institute scholar Christina Hoff Sommers reported:

"In addition to differences in education and training, the review found that women are more likely than men to leave the workforce to take care of children or older parents. They also tend to value family-friendly workplace policies more than men, and will often accept lower salaries in exchange for more benefits. In fact, there were so many differences in pay-related choices that the researchers were unable to specify a residual effect due to discrimination."