From Bloomberg:
In 1986, when the space shuttle Challenger exploded 73 seconds after takeoff, investors immediately dumped the stock of manufacturer Morton Thiokol Inc., which made the O-rings that were eventually blamed for the disaster. With extraordinary wisdom, the global market had quickly rendered a verdict on what happened and why.
Economists often remind us that markets, by pooling information from diverse sources, do a wonderful job of valuing companies, ideas and inventions. So what does the market think about economic theory itself? The answer ought to be rather disconcerting.
Blogger Noah Smith recently did an informal survey to find out if financial firms actually use the “dynamic stochastic general equilibrium” models that encapsulate the dominant thinking about how the economy works. The result? Some do pay a little attention, because they want to predict the actions of central banks that use the models. In their investing, however, very few Wall Street firms find the DSGE models useful.
I heard pretty much the same story in recent meetings with 15 or so leaders of large London investment firms. None thought that the DSGE models offered insight into the workings of the economy.For more on the market reaction to the Challenger disaster see last week's post linking to "The complexity of price discovery in an efficient market: the stock market reaction to the Challenger crash".
This should come as no surprise to anyone who has looked closely at the models. Can an economy of hundreds of millions of individuals and tens of thousands of different firms be distilled into just one household and one firm, which rationally optimize their risk-adjusted discounted expected returns over an infinite future? There is no empirical support for the idea. Indeed, research suggests that the models perform very poorly.
Economists may object that the field has moved on, using more sophisticated models that include more players with heterogeneous behaviors. This is a feint. It isn’t true of the vast majority of research.
Why does the profession want so desperately to hang on to the models? I see two possibilities. Maybe they do capture some deep understanding about how the economy works, an “if, then” relationship so hard to grasp that the world’s financial firms with their smart people and vast resources haven’t yet been able to figure out how to profit from it. I suppose that is conceivable....MORE
Abstract
We provide evidence on the speed and accuracy of price discovery by studying stock returns and trading volume surrounding the crash of the space shuttle Challenger. While the event was widely observed, it took several months for an esteemed panel to determine which of the mechanical components failed during the launch. By contrast, in the period immediately following the crash, securities trading in the four main shuttle contractors seemingly singled out the firm that manufactured the faulty component. We show that price discovery occurred without large trading profits and that much of the price discovery occurred during a trading halt of the firm responsible for the faulty component. Finally, although we document what are arguably quick and accurate movements of the market, we are unable to detect the actual manner in which particular informed traders induced price discovery.
