The table below was published by Martin Prosperity. The data is for deals of $5m-200m from 2010-13 and hence excludes lots of deals that are included in other studies which show a much larger market.
Given that San Francisco and San Jose/Silicon Valley are effectively one market the right way to think about this market is that 19% sits in the winning region, and the rest of venture capital activity is highly fragmented. Here in London we are 1.8% of the total market and just under 10% of Silicon Valley/San Fran combination. That said, we are growing much faster.