Vasco Curdia of the San Francisco Federal Reserve Bank writes: To boost economic growth during the financial crisis, the Federal Reserve aggressively cut the target for its benchmark short-term interest rate, known as the federal funds rate, to near zero around the beginning of 2009. Since then the time projected for the rate to return to more normal historical levels has been continually postponed.
To understand the level of the federal funds rate and when it might be normalized it is useful to consider the concept of the natural rate of interest first proposed by Wicksell in 1898 and introduced into modern macroeconomic models by Woodford (2003). The natural rate of interest is the real, or inflation-adjusted, interest rate that is consistent with an economy at full employment and with stable inflation. If the real interest rate is above (below) the natural rate then monetary conditions are tight (loose) and are likely to lead to underutilization (overutilization) of resources and inflation below (above) its target.
Figure 1
Estimated natural rate of interest (annual rate)
Note: Blue shaded areas represent the range of possible estimates with 70% (darker) and 90% (lighter) probability. Gray bar indicates NBER recession dates.
Figure 1 shows that the natural rate declined substantially during the recession and did not start to recover until the end of 2014. Currently, the median estimate is –2.1%, far below its long-run level of about 2.1%. The fall in the natural rate during the recession is explained by low expected productivity growth. With projected low growth, the economy would need less saving and more spending to use resources fully, hence the lower natural rate of interest. During the economic recovery, the natural rate was kept low by weak demand due to a larger propensity to save in the aftermath of the financial crisis.
Figure 2
Interest rate gap and output gap
Note: Gray bar indicates NBER recession dates.
The large decline in the natural interest rate early in the recession (shown in Figure 1) may explain why the Federal Reserve lowered the federal funds rate so fast in 2008 even before the output gap became negative. Interest rate rules that ignore the variation of the natural rate over time—like the one proposed in Taylor (1993)—would not prescribe dropping the federal funds rate so quickly, which would lead to even tighter monetary conditions and a more negative output gap. Therefore, while monetary policy was accommodative relative to the Taylor rule, it was not accommodative enough to prevent the interest rate gap from increasing and output from falling below potential, as shown in Figure 2.
This model projects that, based on historical relationships, the future interest rate will return to normal too quickly, leading to persistently underutilized resources and output below potential even after the interest rate gap closes.
Figure 3
Real-time estimates of the natural interest rate
The natural rate of interest is expected to remain below its long-run level for some time. This implies that low interest rates over the next few years are consistent with the most efficient use of resources and stable inflation. The analysis also finds that the output gap is expected to remain negative even after the natural rate is close to its long-run level. Additionally, there is considerable uncertainty about both the short-run dynamics as well as what level should be expected in the longer run. All these considerations reinforce the possibility that interest rate normalization will be very gradual. Vasco Curdia of the SF Federal Reserve writes