Sunday, February 1, 2009

if you can’t explain the propensity to hoard, then you can’t explain our current predicament.

From Free Exchange:

"Blanchard roundtable: Where economists fear to tread
Posted by:
The Economist | DELHI
Categories:
Blanchard roundtable

OLIVIER BLANCHARD provides a disturbing account of what Knightian uncertainty means for the economy; let me offer a few untutored thoughts about what it means for economics.

Economists do not, in fact, follow Knight’s work very much. The discipline shys away from his concept of uncertainty (as distinct from risk), because it is, by definition, so hard to model. If economists could model it, then so could firms and investors. The future would be calculable, if not knowable, and there would be less excuse for bewildered inaction.

Paul Samuelson once went so far as to argue that economics must surrender its pretensions to science if it cannot assume the economy is “ergodic”, which is a fancy way of saying that Fortune’s wheel will spin tomorrow much as it did today (and that tomorrow's turn of the wheel is independent of today's). To relax that assumption, Mr Samuelson has argued, is to take the subject “out of the realm of science into the realm of genuine history”.

The scientific pose has great appeal. But this crisis is reminding us again of its intellectual costs. Knightian uncertainty may be fiendishly hard to fathom, but ignoring it, as economists tend to do, makes other phenomena devilishly hard to explain. The thirst for liquidity—the sudden surge in the propensity to hoard—is one example. If risks are calculable, then investors will place their bets and roll the dice. Only if they are incalculable will they try to take their chips off the table altogether, in a desperate scramble for cash (or near-cash). As Keynes put it, “our desire to hold money as a store of wealth is a barometer of the degree of our distrust of our own calculations and conventions concerning the future.”

We journalists make great sport poking fun at the techniques on which financial markets have relied—the value-at-risk models with their normal distributions—much as Keynes scorned all those “pretty polite techniques, made for a well-panelled board room and a nicely regulated market”. But as economists (or as friends of economics) we have to fess up that the models that led banks astray are, fundamentally, ours—they spring from the same intellectual tradition. My suspicion, perhaps unfair, is that in recent years too much macroeconomic theory itself became “one of these pretty, polite techniques which tries to deal with the present by abstracting from the fact that we know very little about the future.”

As Mr Blanchard’s article makes clear, if you can’t explain the propensity to hoard, then you can’t explain our current predicament. And a macroeconomics that cannot explain this crisis is hardly worthy of the name."

Me:
Paul Samuelson once went so far as to argue that economics must surrender its pretensions to science if it cannot assume the economy is “ergodic”, which is a fancy way of saying that Fortune’s wheel will spin tomorrow much as it did today (and that tomorrow's turn of the wheel is independent of today's). To relax that assumption, Mr Samuelson has argued, is to take the subject “out of the realm of science into the realm of genuine history”.

Much of economics is Correlative Explanation and Reasoning. It is not cause and effect. Math can be useful in describing relations, as long as those relations continue to hold. Where behavior is concerned, or any teleological action, you will have correlative reasoning and explanation.

The math models used are simply useful in simple ways. What is shocking is that, compared to the old practitioners of political economy, which will always be the really important realm of understanding these issues, current economists don't seem to have a philosophy of action or math that can explain their assumptions. Consequently, many spit out mechanistic explanations, or versions of dubious psychological theories like behaviorism.

The only way to explain Political Economy is through a Human Agency approach or explanation. The only way to explain hoarding is such an approach. I have found Fisher's Debt-Deflation model to be of great help, but that model also needs a more robust human agency explanation to fill it out.

One famous economist recently mocked Shiller's 'trust' as hard to measure. In saying this, he showed that he had no clear idea of what is involved in a human agency explanation, nor a clear idea of what the limitations of measurement are. It is would interesting to hear the assumptions and presuppositions underlying his basic view of human behavior, if he has one.

Incidentally, I find Bagehot to be still valuable for understanding our current crisis.
2/1/2009 4:25 PM GST

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