The so-called "weak efficient market hypothesis" is more-or-less correct. The "strong efficient market hypothesis" falls apart once you attempt to taboo "efficient".
Another way to phrase this is that in some strict sense market "inefficiencies" exist, finding them is a hard problem. (The general case of this problem is NP-hard.)
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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