Thursday, July 21, 2011

Debt and Delusion

NEW HAVEN – Economists like to talk about thresholds that, if crossed, spell trouble. Usually there is an element of truth in what they say. But the public often overreacts to such talk.

Consider, for example, the debt-to-GDP ratio, much in the news nowadays in Europe and the United States. It is sometimes said, almost in the same breath, that Greece’s debt equals 153% of its annual GDP, and that Greece is insolvent. Couple these statements with recent television footage of Greeks rioting in the street. Now, what does that look like?

Here in the US, it might seem like an image of our future, as public debt comes perilously close to 100% of annual GDP and continues to rise. But maybe this image is just a bit too vivid in our imaginations. Could it be that people think that a country becomes insolvent when its debt exceeds 100% of GDP?

That would clearly be nonsense. After all, debt (which is measured in currency units) and GDP (which is measured in currency units per unit of time) yields a ratio in units of pure time. There is nothing special about using a year as that unit. A year is the time that it takes for the earth to orbit the sun, which, except for seasonal industries like agriculture, has no particular economic significance.

We should remember this from high school science: always pay attention to units of measurement. Get the units wrong and you are totally befuddled.

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  1. I like your unique perspective on the situation, Dr, Shiller. Maybe people are indeed just getting confused over the numbers. Big public debt does not mean small economy.

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  2. That makes perfect sense. Sometimes people compare percentages that should not be associated with each other, just like your example. Then again, I wasn't as financially aware before meeting my loan modification attorney, either.