The decision process in each tiny (but still to complex to model with a computer!) ant brain of what force level to let go and "play dead", to stick together or not, is aggregated into a single number: a viscosity coefficient.
Footnotes:
[1] Recessions and other mass coordination events are the exception, but most of the time, the economy is not in a recession.
The footnote is the reason that macroeconomics is devilishly difficult with respect to prediction. Departures from trend are most significant for prediction and therefore policy, applied macro being political economy. "External shock" (external to the model) is not a satisfying explanation, and it is an admission of failure at prediction, that is, that assumptions are too restrictive to be useful in generating dynamically accurate representational models.
Traders face similar issues in assessing the likely run of a trend (opportunity space), turning points (timing) and the speed and amplitude of swings (volatility). Even though financial investors are dealing with longer term, similar issues apply.
Statistical mechanics of ants
Jason Smith
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