Risk and uncertainty

8 May, 2012 at 14:20 | Posted in Economics, Statistics & Econometrics | 3 Comments

The financial crisis of 2007-08 hit most laymen and economists with surprise. What was it that went wrong with our macroeconomic models, since they obviously did not foresee the collapse or even make it conceivable?

The root of our problem ultimately goes back to how we look upon the data we are handling. In modern neoclassical macroeconomics – dynamic stochastic general equilibrium, new synthesis, new-classical and new-Keynesian – variables are treated as if drawn from a known “data-generating process” that unfolds over time and on which we therefore have access to heaps of historical time-series. If we do not assume that we know the “data-generating process” – if we do not have the “true” model – the whole edifice collapses.

Modern macroeconomics obviously did not anticipate the enormity of the problems that unregulated “efficient” financial markets created. Why? Because it builds on the myth of us knowing the “data-generating process” and that we can describe the variables of our evolving economies as drawn from an urn containing stochastic probability functions with known means and variances.

This is like saying that you are going on a holiday-trip and that you know that the chance the weather being sunny is at least 30%, and that this is enough for you to decide on bringing along your sunglasses or not. You are supposed to be able to calculate the expected utility based on the given probability of sunny weather and make a simple decision of either-or. Uncertainty is reduced to risk.

But this is not always possible. Often we simply do not know. According to one model the chance of sunny weather is perhaps somewhere around 10% and according to another – equally good – model the chance is perhaps somewhere around 40%. We cannot put exact numbers on these assessments. We cannot calculate means and variances. There are no given probability distributions that we can appeal to.

In the end this is what it all boils down to. We all know that many activities, relations, processes and events are of the Keynesian uncertainty-type. The data do not unequivocally single out one decision as the only “rational” one. Neither the economist, nor the deciding individual, can fully pre-specify how people will decide when facing uncertainties and ambiguities that are ontological facts of the way the world works.

Some macroeconomists, however, still want to be able to use their hammer. So they decide to pretend that the world looks like a nail, and pretend that uncertainty can be reduced to risk. So they construct their mathematical models on that assumption. The result: financial crises and economic havoc.

How much better – how much bigger chance that we do not lull us into the comforting thought that we know everything and that everything is measurable and we have everything under control – if instead we would just admit that we often simply do not know, and that we have to live with that uncertainty as well as it goes.

Fooling people into believing that one can cope with an unknown economic future in a way similar to playing at the roulette wheels, is a sure recipe for only one thing – economic catastrophy!

The unknown knowns – the things we fool ourselves to believe we know – often have more dangerous repercussions than the “Black Swans” of Knightian unknown unknowns, something quantitative risk management based on the hypothesis of market efficiency and rational expectations has given ample evidence of during the latest decade.

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3 Comments

  1. “Some macroeconomists, however, still want to be able to use their hammer. So they decide to pretend that the world looks like a nail, and pretend that uncertainty can be reduced to risk. So they construct their mathematical models on that assumption. The result: financial crises and economic havoc.”

    Spot on – especially frustrating are those economists who think the hammer was right but we just weren’t hitting hard enough..

    I’m very much looking forward to Nassim Taleb’s up coming book on anti-fragility and his thoughts on handling risk and uncertainty.

  2. Is the weather analogy really that well founded? People tend to look at weather forecasts — in particular when going on longer trips — and pack accordingly. For instance, when I’m going to Italy in August, I bring more shorts and t-shirts than I would in January. Of course, according to postmodern theory, I have no reason to do so as there is genuine uncertainty which cannot be reduced to risk. Yet, I do it. And many with me. And we are more often than not better equipped than the Keynesians who brought there winter coats as they “simply didn’t know”.

    • I really think the weather analogy works just fine. Relying on actually rather unsubstantiated and overconfident “precise” forecasts may end in nasty surprises for those not taking these forecasts with due reserve, as evidence from both meteorology and finance gives ample proof of.
      [On how people interpret the message in probabilistic weather forecasts Gerd Gigerenzer et al. has an interesting piece here]


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