I read this, and thought I hadn't seen it stated as obviously and clearly before...
â ⦠many [â¦] patterns, even if they did exist, [will] self-destruct in the future ... Suppose, for example, one of the anomalies or predictable patterns appears to be robust. Suppose there is a truly dependable and exploitable January effect, that the stock market [â¦] will generate extraordinary returns during the first five days of January. What will investors do? They will buy on the last day of December, and sell on January 5. But then investors find that the market rallied on the last day of December and so they will need to begin to buy on the next-to-last day of December, and because there is so much âprofit takingâ on January 5, investors will have to sell on January 4 to take advantage of this effect. Thus, to beat the gun, investors will have to be buying earlier and earlier in December and selling earlier and earlier in January so that eventually the pattern will self-destruct. Any truly repetitive and exploitable pattern that can be discovered in the stock market and can be arbitraged away will self-destructâ¦â
[The Efficient Market Hypothesis and Its Critics (Burton G. Malkiel â 2003)]
â ⦠many [â¦] patterns, even if they did exist, [will] self-destruct in the future ... Suppose, for example, one of the anomalies or predictable patterns appears to be robust. Suppose there is a truly dependable and exploitable January effect, that the stock market [â¦] will generate extraordinary returns during the first five days of January. What will investors do? They will buy on the last day of December, and sell on January 5. But then investors find that the market rallied on the last day of December and so they will need to begin to buy on the next-to-last day of December, and because there is so much âprofit takingâ on January 5, investors will have to sell on January 4 to take advantage of this effect. Thus, to beat the gun, investors will have to be buying earlier and earlier in December and selling earlier and earlier in January so that eventually the pattern will self-destruct. Any truly repetitive and exploitable pattern that can be discovered in the stock market and can be arbitraged away will self-destructâ¦â
[The Efficient Market Hypothesis and Its Critics (Burton G. Malkiel â 2003)]