The big problem with the EMH is how easy it is to miss what it actually means: That human behavior, when combined, is aggregating all publicly known information

The big problem with the EMH is how easy it is to miss what it actually means: That human behavior, when combined, is aggregating all publicly known information. So a market can have a price that is a terrible estimate in hindsight, but that's because of hidden information. Pure market speculation is betting on your own personal information being better than the information available at large. If you really have better information, you are improving the quality of the market price. In no way does it mean that going against a market price, or common sense, is asinine: It's just asinine to do so without first getting some special insight. Another common misconception is that it requires perfectly rational market participants, when all it needs is a semblance of rationality in the aggregate: That individual mistakes happen in multiple directions. When that's the case, if people can know that the population is biased in a specific direction on average, the market adapts by providing better returns to the people betting in the opposite direction, which lets them bet harder later. We have plenty of evidence that the EMH works in a general sense: It makes predictions after all, and they are testable. The rise of index funds is, in practice, saying that the EMH is true, and that we have so many people trying to devise the right prices of stocks that we are better off not paying them a dime, and going with their average prediction, saving ourselves the fees. And what do we see? Index fund that perform well enough that they are the biggest investors in pretty much every component in the SP500. And their share will keep growing until so much of the money is in an index that the average fund manager can beat the market by enough to make the fees worthwhile. So I don't see how this hurts researchers and specialists: It just makes them focus on the search for novel information. It's the same when we try to create a new javascript framework, for instance: If web development has stunk for a couple of decades, what is the key insight that everyone else as missed? Without a key, novel insight, it'd all be busywork.