Bloomberg Opinion columnist Barry Ritholtz speaks with the financial theorist and retired neurologist William J. Bernstein, who co-founded the investment management firm Efficient Frontier Advisors and has written several books on finance and economic history. His titles include “The Birth of Plenty: How the Prosperity of the Modern World Was Created,” “A Splendid Exchange: How Trade Shaped the World,” and “Masters of the Word: How Media Shaped History.” He was also the 2017 winner of the James R. Vertin Award from CFA Institute. His latest book is “The Delusions of Crowds: Why People Go Mad in Groups.”