The biggest roadblock holding the economy back right now is deleveraging. Household debt as a percentage of disposable income increased from 59% in 1960 to 130% in 2007. As consumers pare that debt back down to sustainable levels, money that used to be spent on goods and services now goes to debt repayment, fueling less growth than we were used to in the past. That's the simplest, but probably most complete, way to describe why the economy is slow, and why it could stay slow for years.

I recently sat down with Gus Sauter, chief investment officer of the Vanguard Group, one of the world's largest investment companies. He added a unique twist to the deleveraging argument, noting that aging demographics changes how much debt U.S. households can maintain compared with the past. Have a look:

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