Each plan is a little bit different. But the government's General Accounting Office has provided some broad answers, in a study requested by Rep. Barbara Kennelly, D-Conn. Social Security helps low earners by raising their benefit a bit. That wouldn't happen in private accounts. Those accounts might yield more for your money than Social Security does, but the gap between men's and women's retirement income would grow.
Women tend to be more conservative investors than men.
If stocks did poorly for a long period of time, their conservatism would pay. But if stocks did well, their cautious investing would leave them even further behind the retirement incomes drawn by men. Women with the same earnings as men, and the same investments, could wind up with lower monthly incomes. That's because they tend to live longer. They'd have to draw less from their accounts, to be sure the money lasted a lifetime.