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.