Are there any stats available that show the historic performance of YC or TechStars funded companies? I know YC has hit a number of homeruns in Heroku, and AirB

Are there any stats available that show the historic performance of YC or TechStars funded companies? I know YC has hit a number of homeruns in Heroku, and AirBnb, but what is their success rate? 10% 5%?