fallacies with EMHhypothesis
1) that traders (and market participants in general) act RATIONALLY. iow, EMH does not take into account EMOTIONS- fear, panic, greed, euphoria, etc. ANYBODY who has ever traded has seen how emotions can affect trading decisions.
2) that price is merely the digestion of all public data (and in the case of insider trading, private data) available on a company and its security. clearly, all one has to do is look at ANY bubble, or overreaction selloff to see the fallacy that people are merely acting on information. to a large extent (moreso on shorter timeframes, where traders (vs. investors) tend to lurk- in the shortterm people act based on what they think others will do. the only reason one goes long on anything is because they others will do so after them. because that is the only thing that will make the price go up. demand exceeding supply
EMH is a classic example of how "smart" educated academics can circle jerk each other for years over theories that have no basis in reality.