considers security markets as efficient mechanism for immediate and unbiased incorporation of new information into prices. Within the EMH, as argued by Friedman  and Fama , the presence of non-rational traders can be neglected, since their idiosyncratic errors would be averaged out in the aggregate so that they could not significantly affect the market price. Rather, they would progressively lose money in favor of arbitrageurs, betting against them, so that the less rational agents would eventually disappear at the end from the market. Recent empirical and theoretical investigations have attacked the EMH and its implications in various ways. From a theoretical viewpoint, it has been shown that arbitrageurs may have limited capacit
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