Quote from logic_man:
Not only that, but the article states on the first page that the authors take it as proven that under certain assumptions, past price information can be used to make abnormal profits (their phrase), which goes against surf's claim that past prices are useless.
"There are few sophisticated technical rules that may explain why technical analysis works. For example, Treynor and Ferguson (JF, 2985) demonstrate the usefulness of past price information in making an abnormal profit. They develop a Bayesian probability estimate using past price data to assess whether the market incorporates some firm-specific information, that is made available to investors. If the market does not have such information, and this is confirmed in past price data, the investor with this private information can make a trading profit. Technical analysis in the Treynor-Ferguson sense is beyond the scope of this paper, however."