No one seemed to know enough about this to respond before so I did a bit more research on this myself, and decided to post what I found in case anyone was interested. Well, it turns out I was wrong about one thing, I thought the Private Company Index was just starting up but I found a press release on Yahoo saying they were celebrating their 2nd anniversary. The article also says a little about how they keep track of the companies financial info for investors. Lastly it says that so far it has shown a 420% greater return than the average of the Dow, NASDAQ and S&P Small Cap 600 indices performance in the same 24 month period.

Anyways, just wanted to share the information. Hope it is useful to you.

I'm curious - if you invest in companies without public ownership, then how is the ownership of the company calculated in terms of investor interest? After all, going public means the public can invest in owning shares in a company, plus a high level of accountability (in theory, anyway, and certainly a lot more since Enron).

So where does the investor get their rights on non-public companies?