The success rate Paul has had is actually lower than average success rate of small business startups (with more than one employee)
Everyone always quotes a 10% success rate after 1 or 2 years. That is, as Paul suspects, a myth. True success rate is around 66%. Y-combinator's success rate was 50%
Survival and success are two different things. The 50% PG referred to are for the founders becoming "rich" by their standards, not just staying in business.
66% OF SMALL BUSINESS STARTUPS LAST 2 YEARS http://www.smallbiztrends.com/2005/07/business-failure-rates-highest-in.html