"One of the fundamental factors determining whether you borrow or save is your age. If you look at people, households -- younger people, younger households who have a lot of needs (buying a house, buying a car, furniture and so forth) compared to their income, [they] will typically borrow money," he says. "Then when you are older your income is in better shape, your borrowing needs aren’t as great, so you begin to pay that money back.

"So the idea here is if you take that household concept and transfer it to nations, then what we should see is that nations that are younger, that have a higher of higher percentage of younger households, will be net borrowing nations," Walden explains. "Nations that are older will be net savers.

"And, indeed, if you apply this further to the U.S., what you find is the U.S. is a relatively young nation. Our demographic structure is younger than, for example, the nations of Europe, ... Japan and soon to be China. So again taking this a step farther, these economists say it actually makes sense for the U.S. to be a borrowing nation right now, and for other nations to be saving and lending to us, because of this difference in age structure."