DSGE e o teste do mercado

The most damning critique of DSGE, por Noah Smith.

So now let’s get to the point of this post. As far as I’m aware, private-sector firms don’t hire anyone to make DSGE models, implement DSGE models, or even scan the DSGE literature. There are a lot of firms that make macro bets in the finance industry – investment banks, macro hedge funds, bond funds. To my knowledge, none of these firms spends one thin dime on DSGE.

So maybe they’re just using the wrong DSGE models? Maybe they’re using Williamson (2012) instead of Williamson (2013). I mean, after all, there is a huge, vast, unending array of DSGE models out there, most of which purport to explain the entire macroeconomy, and most of which are thus mutually exclusive at any point in time. Maybe two or three of them are right at any given point in time, but maybe this set switches around as conditions change. Perhaps finance-industry people are simple unable to pick out the right DSGE model to use on any given day.

But if finance-industry people can’t know which DSGE model to use, how can policymakers or policy advisors?

In other words, DSGE models (not just “Freshwater” models, I mean the whole kit & caboodle) have failed a key test of usefulness. Their main selling point – satisfying the Lucas critique – should make them very valuable to industry. But industry shuns them.

Many economic technologies pass the industry test. Companies pay people lots of money to useauction theory. Companies pay people lots of money to use vector autoregressions. Companies pay people lots of money to use matching models. But companies do not, as far as I can tell, pay people lots of money to use DSGE to predict the effects of government policy. Maybe this will change someday, but it’s been 32 years, and no one’s touching these things.

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