Evidence and data
Compare the rule with policy rates, inflation gaps, output gaps, and estimates of the neutral real rate.
Calibration or measurement
The neutral rate, inflation target, gap definitions, and response coefficients drive the prescription.
Boundaries
- Neutral-rate uncertainty can dominate the rule.
- Zero-lower-bound settings need extra tools.
- Financial-stability concerns are outside the basic equation.
Use guidance
- When sufficient
- Benchmark policy reaction function for evaluating whether the policy rate is consistent with the central bank's stated inflation and output objectives.
- When sketch only
- Do not use as a literal policy prescription. The rule depends on unobservables: the neutral real rate and potential output. Wrong parameter estimates can flip the rule's verdict on whether policy is tight or accommodative.
- When to switch
- Switch to forecast-targeting rules (Svensson) or to a fully estimated DSGE policy rule when forward-looking inputs matter. Switch to a financial-conditions rule when stress in credit markets is the binding constraint.
- Falsification signal
- A policy rate that systematically deviates from the rule for several years without producing the inflation or output deviation the rule predicts indicates the parameter set (r*, y*) is wrong, not that the rule is wrong.