The Federal Reserve lowered its traditional monetary policy instrument, the federal funds rate, to essentially zero in December 2008. However, economic activity generally depends on interest rates with longer maturities than the overnight fed funds rate. Research shows that interest rates with maturities of two years or more were largely unconstrained by the zero lower bound until at least late 2011. This suggests that, despite the zero bound, the Fed has been able to continue conducting monetary policy through medium- and longer-term interest rates by using forward guidance and large-scale asset purchases.
The Federal Reserve’s main monetary policy instrument is the federal funds rate, which is the interest rate large banks charge each other to borrow reserves overnight. The Fed’s monetary policy committee, the Federal Open Market Committee (FOMC), lowered this rate essentially to zero in December 2008. Thereafter, the FOMC turned to unconventional measures to stimulate the economy, such as large-scale purchases of longer-term government bonds and communication about the future path of the federal funds rate, a practice known as forward guidance (see Williams 2012). This Economic Letter examines how much the near-zero federal funds rate has hindered the Fed’s ability to affect longer-term interest rates.
The federal funds rate vs. longer-term interest rates
The federal funds rate is directly relevant only for financial institutions that trade reserves in the federal funds market. What matters more for the economy is how changes in the fed funds rate pass through to other interest rates that are more relevant for businesses and consumers, such as the prime rate for business loans and interest rates on corporate bonds, auto loans, and mortgages. These loans generally have terms of several months or years, not just one night.
Nevertheless, the Fed can influence medium- and longer term interest rates through changes in the federal funds rate. Bond yields tend to move along with the expectations of financial market participants about the average fed funds rate over the life of the bond. If they didn’t, investors could profit by arbitrage that brought bond yields closer in line with the expected federal funds rate path.
But to what extent has the zero lower bound constraint on the federal funds rate limited the Fed’s ability to influence these longer-term yields? To investigate this question, it is natural to look at U.S. Treasury securities. Treasuries trade more frequently than private-sector debt, providing more timely interest rate data for a wide range of maturities.
The sensitivity of Treasury yields to economic news
In Swanson and Williams (2013), we demonstrate a new way to measure how much the zero lower bound constrains Treasury securities of any maturity. We look at how Treasury securities of different maturities respond to major macroeconomic announcements, such as reports on U.S. employment, gross domestic product, or consumer price inflation. These announcements have important implications for the U.S. economy and future monetary policy, and thus tend to move interest rates of all maturities.
In particular, we estimate the time-varying sensitivity of a given Treasury yield to major macroeconomic announcements relative to a benchmark period when the zero lower bound was not a concern, taken to be 1990–2000. If a particular Treasury yield responds to news today by just as much as it did in the 1990s, then we would say that Treasury yield is unconstrained by the zero lower bound. Alternatively, if a given Treasury yield used to respond to macroeconomic announcements in the 1990s, but no longer responds to those announcements today, then we would say that Treasury yield is completely constrained by the zero bound. A yield could also be partially constrained, that is, respond to news significantly less than normal. This statistical approach provides a rigorous test of whether any given yield is constrained by the zero lower bound and a quantitative measure of how much that yield is constrained.
Figure 1
Sensitivity of three-month Treasury yield to news
Sensitivity of three-month Treasury yield to news
Figure 2
Sensitivity of two-year Treasury yield to news
Sensitivity of two-year Treasury yield to news
Figure 3
Sensitivity of 10-year Treasury yield to news
Sensitivity of 10-year Treasury yield to news
Figures 1 through 3 plot the results of this analysis for three-month, two-year, and 10-year Treasury securities, respectively. The solid blue lines show estimates of how sensitive the particular Treasury yield was to news in recent years, compared with the yield’s average sensitivity in the 1990s. Periods when the blue line is close to the horizontal line at 1 in these figures represent times when that Treasury yield responded fairly normally. Alternatively, periods when the blue line is close to the horizontal line at 0 represent times when that Treasury yield was largely or completely unresp