Discount rate variation is the central organizing question of current asset pricing research. I survey facts, theories and applications. We thought returns were uncorrelated over time, so variation in price-dividend ratios was due to variation in expected cashflows. Now it seems all price-dividend variation corresponds to discount-rate variation. We thought that the cross-section of expected returns came from the CAPM. Now we have a zoo of new factors. I categorize discount-rate theories based on central ingredients and data sources. Discount-rate variation continues to change finance applications, including portfolio theory, accounting, cost of capital, capital structure, compensation, and macroeconomics.
I thank John Campbell, George Constantnides, Doug Diamond, Gene Fama, Zhiguo He, Bryan Kelly, Juhani Linnanmaa, Toby Moskowitz, Lubos Pastor, Monika Piazzesi, Amit Seru, Luis Viceira, Lu Zhang and Guofu Zhou for very helpful comments. I gratefully acknowledge research support from CRSP and outstanding research assistance from Yoshio Nozawa. The views expressed herein are those of the author and do not necessarily reflect the views of the National Bureau of Economic Research.