A new way to measure unconventional monetary policy
Substituting the ‘shadow’ rate for the federal funds rate helps economists better understand how Fed intervention at the zero lower bound affects the economy.

A line chart plotting both the effective federal funds target rate and the researchers’ shadow rate, with percentages on the y-axis and the years of 2003 to 2014 on the x-axis. The lines follow the same path until 2009, after which the effective rate stays just above zero, while the shadow rate drops below zero to negative two-point-five percent.

The ‘shadow’ federal funds rate, unlike the official rate, can move into negative territory.

  • At the height of the Great Recession, the US Federal Reserve pushed the federal funds rate to near zero and then took extraordinary steps to further spark economic growth, such as buying $3 trillion-worth of bonds. It’s been difficult to gauge if these policies have worked, partly because economic models usually rely on the federal funds rate, which can’t fall below zero despite additional monetary stimulus.
  • To measure the effectiveness of the Fed’s unconventional policies, Chicago Booth’s Jing Cynthia Wu and University of California, San Diego, graduate student Fan Dora Xia constructed a “shadow” federal funds rate, which, unlike the official rate, can move into negative territory (see chart).
  • By substituting Wu and Xia’s estimated shadow rate for the effective federal funds rate when it’s at zero, economists can integrate decades of historic data with numbers from the Great Recession.
  • Using the shadow rate, Wu and Xia argue that if the Fed had not intervened once the federal funds rate hit zero, the unemployment rate in December 2013 would have been one percentage point higher than observed.

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