I quite like his parallel with the Roman empire, comparing silver in coins and fertility rate shows a similar pattern indeed.

I would be less convinced by the similarity in the chart showing US monetary policy and birth rate until 1990. I would include also the post-war birth rate spike, which could explain inversely the birth rate quickly declining until 1972 for example, and other events like the Vietnam war or the cold war. But after 1990, the relationship looks convincing. Thank you for sharing these thoughts!