Low interest rate and the next recession

Recently, more people wonder how the central banks would deal with the next recession given that the interest rate is too low.

Central bankers, and many economists, believe that the short-term nominal interest rate is the main or only policy instrument. However, this may not be entirely true. Central banks could use the money supply, by they never did.

Not many central bankers care about money anymore when setting up policy. Certainly, money does not even play a role in their models. I remember Stanley Fischer giving a lecture in Wellington about 20 years ago on the Russian monetary policy after the collapse of the USSR. I wrote in my notes that he said that the central bank brought down inflation by "controlling money and credit."

People may worry about recessions, but they are impossible to predict. Shocks are random. The propagation mechanism of these shocks - the data generating process - is unknown. Even identifying the shocks ex-post is very hard.

The question though is, what happens to real GDP growth (or the output gap) if the short-term nominal interest rate is literally zero? (In fact Milton Friedman argued that the short-term nominal interest rate should be set to zero such that the marginal cost of producing money is equal to the price.)

Consider this simple counterfactual.

In an open-economy - Keynesian - IS curve (i.e., the good market schedule), real GDP growth could depend on its own past (persistence), real interest rate, real exchange rate, and foreign real GDP growth. To carry out the counterfactual, replace the real interest rate with the negative of expected inflation (lag inflation for simplicity) if the nominal interest rate is zero (the Fisher equation). One could choose / estimate the coefficients and calibrate this IS equation with a random normal errors. One could even use a more elaborate Dynamic Stochastic General Equilibrium model to do this counterfactual experiment. Here is one simple counterfactual for New Zealand under such scenario.

The counterfactual suggests that:

-  Real GDP growth could have been higher the actual on average, 4.1 percent compared to 2.6 percent.

-  Real GDP growth could have been less volatile than actual. The variance is 3.1 compared to 4.5

-  The peaks could have been higher and the troughs could have been lower.

-  No recessions detected in the counterfactual.