I'm not quoting anything as proof, I'm marshalling a white paper from 2002 and several other more recent sources as evidence to support my position. As I said in my post, it seems to be hard to come across good evidence that speaks this, but I think the general trend is relatively clear: private funding is a clear and growing majority of all medical research funding, and the largest portion, by far, of both private and public funding is available in the United States.
If you've got more recent evidence that suggests something different, I'd love to hear it - this certainly isn't an issue I've made my mind up on. But I didn't expect to piss people off and get nothing valuable back when I raised this issue that was previously ignored when somebody else brought it up last month. Surely somebody has thought about this.