Interest Rate Conundrums in the Twenty-First Century

Abstract

A large literature argues that long-term nominal interest rates react far more to high-frequency (daily or monthly) movements in short-term rates than is predicted by the standard expectations hypothesis. We find that, since 2000, this high-frequency sensitivity has grown even stronger in U.S. data. By contrast, the association between low-frequency changes (at six- or twelve-month horizons) in short- and long-term rates, which was equally strong before 2000, has weakened substantially. As a result, “conundrums”—defined as six- or twelve-month periods in which short and long rates move in opposite directions—have become increasingly common. We show that this post-2000 combination of high-frequency “excess sensitivity” and low-frequency “decoupling” of short- and long-term rates arises because increases in short rates temporarily raise the term premium on long-term bonds, leading long rates to temporarily overreact to changes in short rates. This post-2000 phenomenon can be understood using a model in which (1) declines in short rates lead to outward shifts in the demand for long-term bonds—for example, because some investors “reach for yield”—and (2) the arbitrage response to these demand shifts is slow. We discuss the implications of our findings for the transmission of monetary policy and the validity of the event-study methodology.

Keywords: interest rates, conundrum, monetary policy transmission

JEL Classification: E43, E52, G12