I think there are two bubbles. We have a stock market bubble and we have a bond market bubble. I think in the end of the day the bond market bubble will be the critical issue. But for the short-term it's not too bad, but we're working obviously towards a major increase in long-term interest rates and that has a very important impact... on the whole structure of the economy.
~ Alan Greenspan, interview on Bloomberg TV, January 31, 2018
(He blamed the bond bubble on fiscal deficits. No mention of the role of central banks.)