U.S. inflation has become sustainably less than the 2% policy target in recent years. As Harvard macro economist Robert Barro indicates, U.S. inflation has remained low and stable since the federal funds rate peaked at 22% in the early-1980s. The Federal Reserve upholds the Taylor interest rate rule that the federal funds rate should increase by more than the next likely rise in inflation. This monetary policy rule accords with the U.S. dual mandate of price stability and maximum sustainable employment. In New Keynesian macroeconomic models, interest rate adjustments can cause real movements in inflation, employment, and the economic output gap due to monopolistic competition and sticky-price persistence.

Former IMF chief economist Olivier Blanchard and his MIT PhD student Jordi Gali show that solo price stabilization would be equivalent to attempting to stabilize both deviations of general prices and economic output gaps from the respective targets. Blanchard and Gali refer to this macroeconomic stabilization principle as the divine coincidence. Nevertheless, the divine coincidence may disappear due to real wage rigidities and financial market frictions. On balance, mainstream macroeconomic models cannot plausibly explain the recent great moderation of low inflation near 1.5%-2% despite gradual and consistent interest rate cycles.