Kenneth Rogoff is Maurits C. Boas Professor at Harvard University and former chief economist at the IMF. His influential 2009 book co-authored with Carmen Reinhart, “This Time Is Different: Eight Centuries of Financial Folly,” shows the quantitative similarities across time and countries in the roots and aftermath of debt and financial crises. His 2016 book “The Curse of Cash” explores the past, present, and future of currency. He has long ranked among the top dozen most cited economists, and is an international grandmaster of chess.