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consilient

That's not what efficiency means in this context. People who say the market is efficient mean one of:

- You can't beat the market

- You can't beat the market without insider information

- You can't beat the market using only information about historical prices.

(Insert "approximately" and "by enough to be worth it" as appropriate)

1 is certainly false, 3 is probably true, 2 is controversial.

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Yeah, I know, but they quoted that one so I used it.

The paper is basically proving 3 can't always be true for actors with unlimited computational power, and without any "approximately" or "by enough to be worth it". It's a cute math trick, not something useful.

You hit the nail on the head, thank you. I probably should have qualified my use of the word "efficient" with "highly" or even "incredibly" to make this more obvious.

The paper doesn't prove you can't be highly efficient in real markets. It proves you can't be perfect.

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