Ask HN: What is the average rate of corporation tax paid by YC Companies?

There is a lot of focus by SV figures these days about philanthropy for social things like schooling, basic income etc. As someone who lives in Ireland and is well aware of the positive/negative effects of tax minimisation by large companies (and the costs that has for small companies here) - I'm curious, what is the average rate of corporation tax paid by YC companies? (Say in the US and/or Europe for example).