Finance and economics: What's wrong with finance | The Economist:
"Mr Lo argues that this approach may sound arbitrary but such behaviour may be is rational from an evolutionary perspective. Take an animal that has a choice of nesting in a valley or a plateau; the valley offers shade from the sun (good for raising offspring) but vulnerability to floods (killing all offspring). The plateau offers protection from floods (good for offspring) but no shade (killing all offspring). The probability of sunshine is 75%. So the “rational” decision from the individual’s perspective would be to stay in the valley. But if a flood occurs, the entire species would be wiped out. It makes more sense for the species if individuals probability match. “When reproductive risk is systematic, natural selection favours randomising behaviour to avoid extinction” he writes.
Mr Lo’s view is that markets are normally efficient but not always and everywhere efficient. He dubs this “adaptive market theory”—and sees it as a consequence of human behaviour, particularly herd instinct. Watching other people suffer triggers an empathetic reaction. When other investors are panicking in a period of market turmoil, we tend to panic too.
A similar approach, dubbed the fractal market hypothesis, is advanced by Dhaval Joshi of BCA Research. This acknowledges that investors with different time horizons interpret the same information differently. “The momentum-based high frequency trader might interpret a sharp one-day sell-off as a sell signal” he says, “but the value-based pension fund might interpret the same information as a buying opportunity. This disagreement will create liquidity without requiring a big price adjustment. Thereby it also fosters market stability.”"
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