[tpudlik]

tl;dr: 1 in 20 would be a better estimate than 1 in 10, but even this underestimates the skew.

Across all VC-funded startups which received first-round funding between 1985 and 2009, 55% were terminated at a loss, and only 6% returned more than 5 times the original investment. But this 6% group generated more than 50% of the gross return across all ventures.

At a "single large and successful" (but, for obvious reasons, anonymous) VC firm which invested about 1 billion over the last decade, about 5% of the total money invested generated a return of 10x or more; almost 60% of the money was invested into companies that terminated at loss.

Source for both assertions: Kerr et al., 2014 (http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2473226)

You may also want to take a look at Figure 2 in Hall and Woodward (2008), which shows the distribution of exit values over 22,000 VC-backed startups founded between 1987 and 2008. About 5% of these startups had exit values of $50 million or more. (http://www.nber.org/papers/w14219)