Hmm. This assumes we know all the spies. But it could be true that spying has been wildly successful, and that most spies were never caught. In a scenario like that, a breakdown of percentages would sound a lot less convincing.

I suppose most spies are caught, but I've always wondered whether Feynman was a spy. Not based on anything in particular; it's just tantalizing to think that random famous people are actually traitors. We'd never know unless they were caught, after all.