There are some threads of ET and there are several books, such as this one: http://www.amazon.com/Evidence-Based-Technical-Analysis-Scientific-Statistical/dp/0470008741 , and this one: http://www.amazon.com/Random-Walk-Down-Wall-Street/dp/0393325350 , which presented strong arguments against technical analysis. Although I do not know the exact methods they test each technical analysis indicators or signals, my guess (and thus my premise for making my argument) is that they threw series of data to each indicator or signal and see whether it makes profit. There are also studies (which I do not recall the author) which have shown that career traders become more successful as their experience grow, and many do use technical analysis. Here is my defense of technical analysis based on the above. All the indicators and signals in technical analysis are like the movements and weapons in martial arts. If my premise were true, then testing series of data on an indicator is like using only one martial art movement such as round house kick, to fight against a variety of enemies regardless whether the enemies come barehanded or with knives or with sticks. How can you survive if all you know is round house kick? Let's say your success rate with round house kick is 50%. Now you test another indicator or another martial art move, such as head punch, against all the data and all the enemies; and you have 49% success rate. And so on, you have tested all the indicators and you conclude that technical analysis or martial arts is no better than flipping a coin. True, technical analysis tries to ignore the fundamentals. But, a big but, humans don't work like robots. People change their strategies, apply different fighting styles and use various indicators or no indicators at all, depending on what they have seen or heard, what news info or new book they read, or what pretty girls they slept with. I guess it is the human factors that are missing when those authors do their "evidence based analysis of technical analysis." And if my premise above if true, then I guess that explains why traders can statistically become more successful with experience, and the fact that there are studies to support this correlation between experience and success, and that many of them do use technical analysis, I must conclude that TA is not useless like coin flip but should be used like martial arts.