In 1993, Stanford economist John Taylor published a paper describing a simple formula that seemed to explain much of the Federal Reserve's post-1980s interest-rate decisions. The formula related the Fed's target rate to two variables: the deviation of inflation from target, and the output gap (the gap between actual and potential GDP). The Taylor Rule, as it came to be known, became one of the most-cited benchmarks in monetary economics — a way to describe what the Fed "should" do and to measure how far actual policy deviated from the rule.
The formula
The classic Taylor Rule can be written as:
r = r* + π + 0.5(π - π*) + 0.5(y - y*)
Where r is the target federal funds rate, r* is the equilibrium real rate, π is current inflation, π* is target inflation (typically 2%), and (y - y*) is the output gap. The two coefficients — 0.5 on the inflation gap and 0.5 on the output gap — are the "reaction function" parameters that describe how strongly policy responds to each deviation.
Plugging in typical values: with a 1% equilibrium real rate, current inflation of 2.5%, and an output gap of 0%, the Rule prescribes a nominal fed funds rate of 1 + 2.5 + 0.5(0.5) + 0.5(0) = 3.75%. If inflation rises to 4% at the same output gap, the prescribed rate rises to 1 + 4 + 0.5(2) + 0 = 6%.
The empirical fit
For the 1987–2007 period, actual Fed policy tracked the Taylor Rule remarkably well. Deviations were typically small and often justified by specific circumstances the rule did not capture. This close fit was one reason the rule became so widely cited — it appeared to describe what the Fed actually did, not just what it should do in theory.
The Federal Reserve staff has for decades tracked several variants of the rule as part of its internal policy analysis, and the FOMC's Summary of Economic Projections (the "dot plot") often shows the median projected rate path aligning broadly with what a Taylor-style rule would prescribe.
Where the rule has broken
Three significant deviations from Taylor-style prescriptions have occurred in the past two decades.
The zero lower bound period. Between 2008 and 2015, the Taylor Rule prescribed a negative fed funds rate for much of the period — sometimes substantially negative. The Fed could not deliver a negative nominal rate through conventional policy (though it debated the question extensively), so it used unconventional tools: quantitative easing, forward guidance, and eventually explicit lower-bound commitments. Actual policy deviated from the rule because the rule's prescription was infeasible.
The 2020–2021 pandemic response. The Fed maintained very accommodative policy through much of 2020 and 2021 even as inflation accelerated. A strict Taylor Rule reading would have prescribed rate increases earlier and more aggressively than the Fed delivered. This deviation was later described by many observers, including some Fed officials, as an error — the "transitory" framing of pandemic inflation delayed the response beyond what a rule-based approach would have produced.
The 2022–2024 tightening cycle. The Fed's rapid rate increases during this period were, at first, broadly consistent with what an aggressive Taylor Rule variant would have prescribed. But the Fed continued tightening beyond the point where several rule variants would have prescribed pauses, and later maintained rates at high levels longer than most rule variants suggested. This "higher for longer" policy reflected the Fed's discretionary judgment about inflation expectations rather than a mechanical reading of the rule.
The rule's fundamental limits
Beyond the specific deviations, the Taylor Rule has structural limits that constrain its usefulness as a real-time policy guide.
The output gap is unobservable. Potential GDP is not a directly measurable quantity — it must be estimated, and different estimation methods produce substantially different results. A rule that depends on estimated output gaps carries the estimation error into its prescription, sometimes producing wide ranges of "correct" policy rates depending on which estimate is used.
The equilibrium real rate is unobservable. R-star (r*) is even harder to estimate than the output gap. Fed staff estimates of r-star have varied by more than a percentage point over the past decade, and the recent Fed has been openly uncertain about whether r-star has structurally risen from its very low 2010s levels.
Inflation expectations matter beyond current inflation. The rule uses current inflation as its input, but modern monetary theory emphasises the importance of anchored inflation expectations. If expectations are well-anchored, the Fed has more flexibility to look through temporary inflation deviations; if expectations are becoming unanchored, the Fed must respond more aggressively to any inflation move regardless of what current data suggests.
The rule does not incorporate financial conditions. Monetary policy affects the economy substantially through financial conditions (credit spreads, equity prices, exchange rates) as well as through the direct rate channel. When financial conditions are unusually tight or unusually loose relative to what the policy rate would suggest, the Fed may adjust rates to offset. The Taylor Rule captures none of this.
What the rule is still useful for
Despite its limits, the Taylor Rule provides a useful benchmark for understanding Fed decisions and communicating them to broader audiences. When the Fed's actual rate substantially differs from a range of Taylor-style prescriptions, the deviation itself is informative — it suggests the Fed is applying judgment about something the rule does not capture.
Reading Fed communication through the lens of Taylor-style variants helps identify what the FOMC is emphasising. When the median dot rises significantly above what standard rules would prescribe, the Committee is signalling concern about something the rule misses — most often inflation expectations or financial stability. When it falls significantly below, the Committee is signalling concern about downside risks.
The rule to internalise
The Taylor Rule is not a policy prescription; it is an analytical benchmark. Understanding what it says provides a stable reference point for reading actual Fed policy — deviations from the rule are informative signals about what the Committee is judging that the rule does not capture. The rule's limits are as important as its formulation: any policy prescription depending on unobservable variables (potential GDP, r-star, anchored inflation expectations) carries irreducible uncertainty that a mechanical rule cannot resolve.
Educational content only. Not investment advice.