Most of them aren't hedge funds, they're private (HFT, Electronic Trading, Botique Firms, Proprietary Trading are all terms you'll hear) so they don't have public data. It is literally impossible to prove without insider information.

However the Virtu Financials, the Citadels, etc, will always exist, and will be doing exceptionally well whether people realize it or not.

Yeah, a better name for these kinds of funds is "independent research groups." Edgestream is an example of another. Renaissance is the most (in)famous one, but many others exist which profitably manage tens to low hundreds of billions while employing only 10 - 100 people.

I realize this doesn't actually matter and I feel weird defending Renaissance... but Virtu is a public company and hasn't been doing that well, and returns from Citadel's various funds are not hard to find. Also, I don't know how to compare a fund's returns to that of a private business. But Medallion has been around since before HFT was really a thing, and I'm not aware of any HFT places that have been growing at 70% a year for 20 years.

These are wildly different businesses. Virtu is a global electronic market maker which in reality is more like a mature technology company than a risk taking hedge fund. Renaissance (Medallion specifically) is a weird fund that manages employee money. Citadel is a large, diversified financial services company that happens to have overlap with both of the previously mentioned firms. They have a large market making operation and offer a variety of different hedge funds that they market

It's not unheard of for market makers to have returns well above 100%, and one you get into certain latency arbitrage strategies the returns can grow significantly.

The issue is that these business are capital limited, so you can't reinvest your massive returns to compound them.