But there's one demographic where women outearn men: people who are single, childless, and between the ages of 22 and 30.

  Within that universe, U.S. women earn 8 percent more than men, on average, according to a new report from the research firm Reach Advisors.

  Women in this group out-earn men by an even larger margin in some metro areas -- 17 percent in New York, 11 percent in San Francisco, and a high of 21 percent in Atlanta, to name a few.