Medallion has probably gotten more scrutiny than any other fund, yet 3 decades later it's still as opaque as ever beyond vague 'statistical methods'. It makes a lot of money no matter what. It's more tight-lipped and exclusive than Jane Street. I don't even think anyone knows even if it's doing market making or not. Or if it's making short-term directional bets. You would think after 30 years stuff would leak and the edge would be gone. Employees are paid enough to not disclose, and likely are divulged only a small part of the overall method/system, so only a handful of employees will know how it works in its entirety. What it's doing has to be on a very large scale and in a big and liquid market to be so consistent and profitable.