By observing multiple people who have done either thing for 10+ years.
Sure, there might be lots of confounding factors, and it might not be causation at all. That's why the quote is from a speech, not a paper
Sure, there might be lots of confounding factors, and it might not be causation at all. That's why the quote is from a speech, not a paper
> What can be asserted without evidence can also be dismissed without evidence.
quotes like this are only used to dismiss observations you don't like
I observe so many ways to have known and unknown bias in this I call any outcomes cow manure.