It'd be interesting to see hard data on that, from speaking with various YC founders in recent batches it seems a lot of them had recommendations from YC alumni

It'd be interesting to see hard data on that, from speaking with various YC founders in recent batches it seems a lot of them had recommendations from YC alumni. Back in the early days pg mentioned around 10-15% of the accepted class were referred but I wouldn't be surprised if that figure had crept up over time.