But if a proportion of the other 900 companies are more successful that the 100 accepted companies, it provides some insight into the ability of YC to pick 'winners'. Particularly if a company that is turned down out perfoms a YC company in the same space/field.
Not necessarily; it could be that YC helps companies become winners (which it certainly professes to.) But both YC's ability to pick winners and their helpfulness to the chosen few would be disproved if there was no difference between rejected and accepted applicants.
