The "motherhood wage penalty" refers to the finding that women in the workplace who become mothers tend to receive fewer benefits (or even a reduction in benefits) compared with non-mothers. In an audit study conducted Shelley Correll and colleagues, applications were sent to various employers over an 18-month period (Correll, Benard, and Paik, 2007). The data revealed that childless women received more callbacks for jobs than mothers did. In addition, a lab experiment investigating the same factors found that participants recommended a significantly lower salary for mothers than for non-mothers, in addition to rating them as less competent and committed. Interestingly, fathers were recommended a higher salary and were rated as more committed than were non-fathers. (In the audit study, fathers received marginally more callbacks than non-fathers did, but this effect didn't reach significance.) Taken together, men and childless women experience benefits in the workplace compared with mothers -- heterosexual mothers, that is. Lesbian parents, however, appear to experience a "lesbian wage premium."
Indeed, research by Amanda Baumle (2009) revealed that while straight women with children earn from about 2- to 4-percent less than straight women without children did, lesbians with children earn about 20-percent more than lesbians without children did.
Understanding this requires that we consider the influence of gender role expectations and sexual orientation stereotypes. With regard to gender roles, many men have yet to accept a world with more women in positions of power, or even one with more women as household breadwinners. "Role congruity theory" asserts that the disparity between men and women in the workplace may be due to male employers seeing women in the labor force as incongruent with their expectations for masculinity. To the degree that some businesses still view women as inherently nurturing and preoccupied with family, they may be exceptionally reluctant to invest in those who have children, as it may magnify or validate the stereotype in their minds. Thus, they discriminate against mothers by favoring non-mothers because the stereotype of femininity isn't as salient.
It is this same gender-role-based sexism that leads to advantages for men and lesbians, albeit for different reasons. As reported by Correll et al. (2007), men are seen as more committed once they become fathers, presumably because they are going to take work more seriously to care for their family. It is important to note that the effect for men can be explained entirely by gender role stereotypes as opposed to sexual orientation, as Baumle (2009) found that salaries for both straight men with children and gay men with children are about 7- to 16-percent higher than for non-fathers.
For lesbians, however, there is an interaction between sexual orientation and biological sex. Lesbians may experience a "motherhood wage premium" due to employers using sexual orientation-based stereotypes; specifically, they may view lesbians as less feminine or more masculine than heterosexual women. As a result, lesbians with children are treated the same way as fathers (by being paid more than lesbians without children) and non-mothers. This likely explains the dozen or so studies finding that lesbians earn more than straight women. At the same time, lesbians experience a gender pay gap similar to heterosexual women.
While lesbians are paid more than straight women, they only earn $0.81 to $0.79 for every $1 a gay or straight man makes, respectively. Moreover, while a man may see his family lose $11,084 each year because his wife is being paid less, a lesbian may see her family lose $20,404 each year because both she and her wife are being paid less. Thus, by not passing the Paycheck Fairness Act and allowing the gender pay gap to continue, wife-wife families are being disadvantaged in a way that is not true for husband-wife or husband-husband families.
These findings raise two legal concerns, one that is extraordinarily clear and long-overdue, and another that may seem counterintuitive given the research findings reported. First, the Paycheck Fairness Act is necessary for both heterosexual women and lesbians. The $11,084 that heterosexual women are shortchanged each year can lead to make-or-break financial decisions for their families (which is why husbands should support equal pay as much as their wives do). At the same, the combined finances out of which lesbian spouses are cheated raises the same challenges that interracial-minority (e.g., Asian-black, Latino-Indian, etc.) families face. Lastly, the Employment Non-Discrimination Act (ENDA) will need to be passed in quick succession, if not at the same time as the Paycheck Fairness Act. This is because employers who paid women less before, and especially those who reside in states where it's actually legal to fire someone for being lesbian or gay, may be all the more tempted to discriminate against lesbian or gay employees. And while there's evidence of more occupational benefits for being out at work rather than concealing sexual orientation, we've yet to see if states that are not gay-friendly will respond to the DOMA ruling by discriminating against their lesbian and gay employees (especially those that married in an equality state and relocated to a non-equality state). Assuming that employers in those states defended their discriminatory actions as being related more to sexual orientation than to biological sex, there may be no legal recourse outside passing ENDA.