Inconsistencies with Other Market Hypotheses
The Efficient Market Hypothesis
The efficient market hypothesis (EMH) concludes that technical analysis cannot be effective. According to this hypothesis, all relevant information is quickly reflected in a security's price through the actions of traders who have that information. Thus, it is impossible to "beat the market," and technical analysis cannot work. News events and new fundamental developments which influence prices occur randomly and are unknowable in advance. Advocates of EMH have produced many studies that reject the efficacy of technical analysis.
Proponents of technical analysis counter that technical analysis does not completely contradict the efficient market hypothesis. Technicians agree with EMH in that they believe that all available information is reflected within a security's price; that is why technicians say a study of the price movement is necessary. Technicians argue that EMH ignores the realities of the market place, namely that many investors base their future expectations on past earnings, track records, etc. Because future stock prices can be strongly influenced by investor expectations, technicians claim it only follows that past prices can influence future prices.
Technicians point to the new field of behavioral finance. Behavioral finance essentially says that people are not the rational participants EMH makes them out to be. Market participants can and do act irrationally. Technicians have long held that irrational human behavior influences stock prices and claim to have ways of predicting probable outcomes based on this behavior.
The Random Walk Hypothesis
The random walk hypothesis is also at odds with technical analysis and charting. Essentially, the hypothesis claims that stock price moments are a Brownian Motion with either independent or uncorrelated increments. In this model, movements in stock prices are not dependent on past stock prices, so trends cannot exist and technical analysis has no basis. Again, proponents of this theory have generated substantial research in support of the hypothesis.
The random walk hypothesis may be derived from the weak-form efficient markets hypothesis, which is based on the assumption that market participants take full account of any information contained in past price movements (but not necessarily other public information).
Technical analysts maintain that trends are identifiable in the market and that it is impractical to believe that market prices move in a random fashion. To a technician, over time prices will trend in a direction until supply equals demand. Therefore, there cannot be any pure random price movement. As stated earlier, one of the cornerstones of technical analysis is that prices trend. If one does not believe this concept, one will not agree with technical analysis.
Also, with regards to EMH and Random Walk Theory, technicians claim that both theories ignore the realities of the marketplace. To a technician, the market is neither composed of completely rational participants as EMH assumes (participants can be greedy, overly risky, etc. at any given time) nor is its stock price movement completely independent of its prior movement (technicians will point at charts like AOL above). Technicians maintain that both theories would also invalidate numerous other trading strategies such as index arbitrage, statistical arbitrage and many other trading systems.
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