I frequently see the stat that YC companies are worth 30 billion in total. While this is very impressive, it's still less than say Uber at 40 billion for a single company that's about the median age of the group--so it seems like a fair comparison, though an obvious outlier.

For the Uber, Twitter, Facebook, Google, etc. outlier startups, how much pure luck do you think plays into their success? AirBnB and Dropbox are YC's biggest outliers. Have you found any actionable patterns in the way the founders of these outliers work/think/operate compared with the more moderately successfully and unsuccessful founders?