I'm coming around on the stronger version of the Efficient Market Hypothesis that says, "you can't buy and sell equities in a way that beats the market in the long run. Just invest in an index fund, pay low fees, and don't try to pick stocks." I'm not sure I believe this any more, for a few reasons.

One is that I lived with a guy who traded professionally and we had a series of conversations where he explained about stocks to me, specifically why information-efficient prices don't automatically imply an unbeatable market.

Another is that the outside-view strong-EMH argument has some vague structural similarities to arguments I hear about poker being unbeatable, with the following facts that seem VERY reminiscent of trading:

• The long run is so long and the variance so high that day-to-day performance is basically all noise, and so
• Lots of players with losing strategies appear to beat the games, and
• Lots of players with winning strategies lose money, even over "long" periods of time, and THEREFORE
• Just because someone has won in the past doesn't mean you can do what they do and make money.

But I know that poker is in fact beatable, I know why it's beatable, and I know it because of specific facts about the reality of the games & the players. Similarly I suspect that certain facts about real markets and market actors may make them beatable by retail investors.

Still researching this.