David O. Lucca and Emanuel Moench
For many years, economists have struggled to explain the “equity premium puzzle”—the fact that the average return on stocks is larger than what would be expected to compensate for their riskiness. In this post, which draws on our recent New York Fed staff report, we deepen the puzzle further. We show that since 1994, more than 80 percent of the equity premium on U.S. stocks has been earned over the twenty-four hours preceding scheduled Federal Open Market Committee (FOMC) announcements (which occur only eight times a year)—a phenomenon we call the pre-FOMC announcement “drift.”
The equity premium is usually measured as the difference between the average return on the stock market and the yield on short-term government bonds. Previous research on the size of the premium finds that it is too large for plausible levels of risk aversion (see Mehra  for a review).
The Drift: A First Take
The pre-FOMC announcement drift is best summarized in the chart below, which provides two main takeaways:
- Since 1994, there has been a large and statistically significant excess return on equities on days of scheduled FOMC announcements.
- This return is earned ahead of the announcement, so it is not related to the immediate realization of monetary policy actions.
The chart shows average cumulative returns on the S&P 500 stock market index over different three-day windows. The solid black line displays the average cumulative return starting at the market’s opening on the day before each scheduled FOMC announcement to the market’s close on the day after each announcement. Our sample period starts in 1994, when the Federal Reserve began announcing its target for the federal funds rate regularly at around 2:15 p.m., and ends in 2011. (For a list of announcement dates, see the FOMC calendars.) The shaded blue area displays the 95 percent confidence intervals around the average cumulative returns—a measure of statistical uncertainty around the average return. We see from the chart that equity valuations tend to rise in the afternoon of the day before FOMC announcements and rise even more sharply on the morning of FOMC announcement days. The vertical red line indicates 2:15 p.m. Eastern time (ET), which is when the FOMC statement is typically released. Following the announcement, equity prices may fluctuate widely, but on balance, they end the day at about their 2 p.m. level, 50 basis points higher than when the market opened on the day before the FOMC announcement.
How do these returns compare with returns on all other days over the sample period? The dashed black line, which represents the average cumulative return over all other three-day windows, shows that returns hover around zero. This implies that since 1994, returns are essentially flat if the three-day windows around scheduled FOMC announcement days are excluded.
A Deeper Look through Regression Analysis
The previous chart showed stock returns without accounting for dividends or the return on riskless alternative investments. In the table below, we account for these factors in a regression analysis by considering the return, including dividends (in percent), on the S&P 500 index in excess of the daily yield on a one-month Treasury bill rate, which is a measure of a risk-free rate. We regress this “excess return” on a constant and on a “dummy” variable, equal to 1 on days of FOMC announcements.
The coefficient on the constant (second row) measures the average return on non-FOMC days, while the coefficient on the FOMC dummy (top row) is the differential mean return on FOMC days. In the first column, we regress close-to-close stock returns and see that excess returns on FOMC days average about 33 basis points, compared with an average excess return of about 1 basis point on all other days. As seen in the previous chart, this return is essentially earned ahead of the announcement—hence our label of a pre-FOMC announcement drift. Indeed, in the third column we see a return of about 49 basis points during a 2 p.m.-to-2 p.m. window, while the FOMC releases its statement at 2:15 p.m. ET. In the second column, we repeat the regression using the close-to-close returns from 1970 to 1993, which is prior to when the Fed released its policy decisions right after each meeting, and see that essentially no such premium exists. The bottom rows of the table decompose the annual excess return of the S&P 500 index over Treasury bills on the return earned on FOMC days and the return earned on all other days. As shown in the third column, the return on the twenty-four-hour period ahead of the FOMC announcement cumulated to about 3.9 percent per year, compared with only about 90 basis points on all other days. In other words, more than 80 percent of the annual equity premium has been earned over the twenty-four hours preceding scheduled FOMC announcements, which occur only eight times per year.
The chart below visualizes this return decomposition. It shows the S&P 500 index level along with an S&P 500 index that one would have obtained when excluding from the sample returns on all 2 p.m.-to-2 p.m. windows ahead of scheduled FOMC announcements. In a nutshell, the figure shows that in the sample period the bulk of the rise in U.S. stock prices has been earned in the twenty-four hours preceding scheduled U.S. monetary policy announcements.
An International Perspective
Does this striking result apply only to U.S. stocks? While we do not find similar responses of major international stock indexes ahead of their respective central bank monetary policy announcements, we observe that several indexes do display a pre-FOMC announcement drift, as the chart below shows. Cumulative returns rise for the British FTSE 100, German DAX, French CAC 40, Swiss SMI, Spanish IBEX, and Canadian TSE index when each exchange is open for trading over windows of time around each FOMC announcement in our sample.
One might expect similar patterns to be evident also in other major asset classes, such as short-and long-term fixed-income instruments and exchange rates. Surprisingly, though, we don’t find any differential returns for these assets on FOMC days compared with other days. In other words, the pre-FOMC drift is restricted to equities. Further, we don’t find analogous drifts ahead of other macroeconomic news releases, such as the employment report, GDP and initial claims, among many others. The effect is therefore restricted to FOMC, rather than other macroeconomic, announcements. In the Staff Report, we attempt to account for standard measures considered in the economic literature that proxy for different sources of risk, such as volatility and liquidity, but they also fail to explain the return. Finally, we consider alternative theories that feature political risk, investors with capacity constraints in processing information, as well as models where stock market participation varies over time. Although these theories can help qualitatively explain the existence of a price drift ahead of FOMC announcements, they are counterfactual in some dimension of the empirical evidence.
Our findings suggest that the pre-FOMC announcement drift may be key to understanding the equity premium puzzle since 1994. However, at this point, the drift remains a puzzle.
The views expressed in this blog are those of the authors and do not necessarily reflect the position of the Federal Reserve Bank of New York, or the Federal Reserve System. Any errors or omissions are the responsibility of the authors.