Why are we so much wealthier now than at any other point in human history? Deirdre N. McCloskey explains this in her Bourgeois Era book series, which she summarizes in this interview. It is worth the listen. In 1800 the average income per day was $3 and today in the US is $130. How to explain this? (And yes, the $3 is income in today’s dollars, adjusted for inflation). Her explanation? Ideas! Not labor or capital but the free exchange of ideas.