“But as women’s careers and earnings have taken off, their contributions have swelled Social Security’s coffers. “Men and women are living longer, and women’s contributions to the system have paid for that,” Mulligan says. “When Social Security was founded, people weren’t expected to be retired for a third of their lives.”

Cynthia Hess, of the Washington-based Institute for Women’s Policy Research, says benefits are especially important to women because they tend to outlive men and are less likely to have other retirement income.