Document Type

Working Paper

Publication Date



In an efficient market, technical analysis cannot earn abnormal returns. Technical strategies are inferior to a buy and hold strategy since they typically churn investor accounts. Nonetheless, technical analysis appears to thrive. The purpose of this paper is to explain why technical analysis survives even though it is inferior to a buy-and-hold strategy. A model is developed that compares four investor groups --informed insiders, buy-and-hold investors, technical traders, and uninformed naive fundamental traders --and are comparedin the model. Surprisingly, it demonstrates the superiority of technical analysis relative to fundamental analysis. The equilibrium requires that different classes of investors earn different rates of return. Informed traders can only earn sufficient returns to cover their costs if there exist traders who, in some sense, are trading on bad information or "noise" in the Fisher Black sense. The ultimate explanation for the survival of naive investment strategies is that informed traders must have someone with whom to trade. If all uninformed traders are driven out of the market there is no benefit to being informed.