Markets After the Age of Efficiency
As anyone who has taken Finance 101 knows, there are three versions of the efficient market hypothesis. The strong version claims that everything you might know about the value of securities is “in the price”. It is closely bound up with the idea of rational expectations, whose implications have dominated macroeconomics for 30 years. Policy interventions are mostly futile, monetary policy should follow simple rigid rules, market prices are a considered reflection of fundamental values and there can be no such things as asset-price bubbles.
These claims are not just empirically false but contain inherent contradictions. If prices reflect all available information, why would anyone trouble to obtain the information they reflect? If markets are informationally efficient, why is there so much trade between people who take different views of the same future? If the theory were true, the activities it purports to explain would barely exist.
Yet although efficient market theory is not true, it may nevertheless be illuminating. The absurdities of rational expectations come from the physics envy of many economists, who mistake occasional insights for universal truths. Economic models are illustrations and metaphors, and cannot be comprehensive descriptions even of the part of the world they describe. There is plenty to be learnt from the theory if you do not take it too seriously – and, like Mr Buffett, focus on the infrequent inefficiency rather than the frequent efficiency.
…The strong version of the efficient market hypothesis is popular because the world it describes is free of extraneous social, political and cultural influences. Yet if reality were shaped by beliefs about the world, not only would we need to investigate how beliefs are formed and influenced – something economists do not want to do – but models and predictions would be contingent on these beliefs. Of course, models and predictions are so contingent, and an understanding of how beliefs form is indispensable. Economics is not so much the queen of the social sciences but the servant, and needs to base itself on anthropology, psychology – and the sociology of ideologies. The future of investing – and economics – lies in that more eclectic vision.
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Further reading: Culture and Prosperity: Why Some Nations Are Rich but Most Remain Poor
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