Millions of Americans rely on Social Security for much of their retirement income. But acting Social Security Administration Commissioner Carolyn Colvin thinks women are particularly at risk for not having enough income in retirement, and she's urging women to save earlier, and more, to make sure they have enough money to make ends meet after they retire.

In the following video, Dan Caplinger, The Motley Fool's director of investment planning, takes a closer look at Colvin's comments. The general idea of what the SSA commissioner says is simple: Women have longer life expectancies, and so they need more savings. Yet Colvin notes that the average woman's Social Security benefits are lower -- about $13,000 per year, compared with $17,000 for men. Dan looks at why that's the case and notes that in many circumstances, women rely on key decisions that their spouses make that can have a huge impact on their Social Security benefits. Dan concludes that the best way to go forward is to have outside savings to supplement Social Security income.

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