Yes, it is very difficult to actually judge skill versus just survivor-ship bias. I worked for a hedge fund that had around $20B under management, lost 60% in 2

Yes, it is very difficult to actually judge skill versus just survivor-ship bias. I worked for a hedge fund that had around $20B under management, lost 60% in 2008, then made all of that back in 18-24 months. Now, they're worth 50% more than loss. Are they skilled? I don't know.