I'm not 100% sure this is what's happening, but thought I'd share my experience: I used to work at a hedge fund that sometimes held stakes in private companies. Every year, we would have to mark the stakes to market. However, we could not do the valuation ourselves; the valuation was done by 3rd party auditors. And these 3rd party auditors usually have no idea what they are doing. Even if they are Big 4 auditors and the stakes are large :/