I’ve posted on this question before, even written papers about it. Rather than rehash all that, I direct you to a very nice post by John Sides at The Monkey Cage.
If you don’t know, The Monkey Cage is, roughly speaking, the TIE of political science, bringing research evidence to bear on policy through a political science, rather than health economics/health services research lens as we do here. A belated kudos to Sides for his blogger of the year award.