What Is the Taylor Rule — A Formula for Calculating the Appropriate Rate
"How exactly does a central bank set rates?" One answer to this question was given by the Taylor Rule. It is a formula that calculates the appropriate rate when you plug in prices and economic conditions.
What Is the Taylor Rule?
The Taylor Rule is a formula proposed by economist John B. Taylor in his 1993 paper "Discretion versus policy rules in practice."
The core idea is simple. A central bank's appropriate policy rate can be calculated from "how much prices are above the target" and "how much hotter the economy is than its potential level (the output gap)."
A Look at the Formula
The basic form of the Taylor Rule is as follows.
Appropriate rate = (neutral real rate + current inflation rate) + 0.5 × (inflation rate − inflation target) + 0.5 × (output gap)
Put in words, it is a rule that if prices are 1 percentage point above target, you raise the rate by 0.5 percentage points more, and if the economy is hotter than its potential, you tighten that much more (the coefficients in the original paper are 0.5 and 0.5).
In other words, it puts the common-sense idea of "if prices are hot, raise rates to cool them; if the economy cools, lower rates to warm it" into numbers.
The 0.5 coefficient and the values for the neutral rate and target inflation vary by assumption. Even with the same rule, the result changes greatly depending on which values you plug in.
Why Central Banks Don't Follow It As Is
The Taylor Rule is a useful benchmark for gauging "whether rates are at an appropriate level now." But actual central banks do not follow this formula mechanically.
The neutral rate and the output gap cannot be known exactly in real time (they are estimates), and in exceptional situations such as a financial crisis or a pandemic, judgment outside the formula is needed.
So the Taylor Rule is used not as a "correct answer" but as a "reference yardstick." It is used in ways such as assessing that "policy is accommodative/tightening" when the actual rate is much lower or higher than the rule.
常见问题
Q. If I just know the Taylor Rule, can I predict rates?
No. The rule is only a reference benchmark; central banks actually add many judgments. Moreover, the inputs themselves, such as the neutral rate and the output gap, are estimates, so they come out differently for different people. The rule is a tool for "assessing" rates, not a magic formula for "predicting" them.
Q. What is the output gap?
It is the difference between the economy's potential output level and its actual output level. If actual is greater than potential, the economy is seen as overheating (a positive gap); if smaller, as in recession (a negative gap). But because the potential level itself is an estimate, it is hard to calculate exactly.
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