[bostik]

Medallion has been closed for new investors since ... a long time ago. Nobody has an explanation how they can sustain such an absurd return, but there are a few theories floating around.

Subjectively the one that appeals most to me, is that the fund has an investment strategy built around their ability to identify and capture very specific types of opportunities - and that there are only so many of them globally in any given year. This puts an upper bound to how much the fund even can invest, because their strategy works for scenarios that are limited both in size and frequency.

[JacKTrocinskI]

I think that makes sense and it also shows that an algorithm can in practice reliably find market inefficiencies and solve them in some scenarios. In those cases a free market can exist but the robot will always beat it and eventually discourage all other market participants from participating, essentially creating a sort of communist economic system for that particular market.