The Fed Reaction Function: How the Federal Reserve Actually Decides on Rates

By Ken Chigbo, founder of KenMacro, updated 2026-06-10. A macro desk’s plain-English guide. Educational only, not financial advice.

What a reaction function actually is

A reaction function is the link between what the economy does and what the central bank does about it. The Fed does not set rates by mood. It runs a broadly predictable response: inflation runs hot, policy leans tighter; the labour market weakens, policy leans easier. The reaction function is the desk’s name for that response, the mental model that turns a data print into a rate decision.

The point that trips most retail traders is this. Markets do not move on the data alone. They move on the data relative to what the Fed was expected to do about it. A strong jobs number only matters if it shifts where the Fed is likely to land. If you only watch the headline and ignore the function that processes it, you are reading half the page. Model the function and the same print tells you where the dollar and the front end of the curve go next.

The dual mandate: price stability and maximum employment

Congress gives the Fed two jobs: stable prices and maximum employment. Those are the two dials on the panel. Price stability is anchored on a 2 percent inflation target, measured on core PCE so that volatile food and energy do not jerk the policy around. Maximum employment is the highest level of jobs the economy can sustain without inflation building, and the Fed reads it off unemployment, payroll growth, participation and wages.

Most of the time the two dials point the same way and the job is easy. The hard regime is when they conflict: inflation above target while the labour market also softens. Then the Fed has to weigh which mandate is further from goal and which it can fix faster. That trade-off is the heart of the reaction function, and it is exactly where the desk earns its keep, because the market is forced to guess which mandate the committee prioritises.

The inputs the Fed weighs

Start with core inflation. The Fed cares about the underlying, persistent rate, not a single hot or soft headline. It strips out food and energy and watches the trend over several months, with a close eye on the stickier services components that signal whether high prices have become embedded.

Inflation expectations sit right behind it, and they may matter more than any single print. If households and markets still believe inflation returns to 2 percent, the Fed has room to be patient. If expectations drift up, the Fed has to act hard to defend its credibility, because once expectations un-anchor, inflation feeds itself. Survey measures and market-implied breakevens are watched obsessively for that reason.

Then the labour market: payrolls, the unemployment rate, participation and wage growth. Wages are the bridge between jobs and inflation, so fast wage growth with full employment reads as inflationary and pushes the function hawkish. Last comes financial conditions: the dollar, credit spreads, equity levels and real yields. Tighter conditions do some of the Fed’s work for it and can let it sit still; easier conditions can force it to lean harder than the data alone would suggest.

The Taylor rule intuition

The Taylor rule is the simplest way to write a reaction function down. In plain terms it says the policy rate should equal a neutral rate, plus a response to how far inflation sits above target, plus a response to how far output or employment sits from its sustainable level. Inflation a point above target, the rule says lift rates more than one for one so that the real rate actually rises and bites. A weak labour market, the rule says cut.

The Fed does not mechanically follow any single Taylor rule, and it says so. But the intuition is the spine of the whole exercise: rates respond to gaps from goal, and the response to inflation has to be aggressive enough to keep real rates moving in the right direction. When you hear a policymaker talk about getting rates to a level that is sufficiently restrictive, that is Taylor-rule language. Run the rule yourself on the latest inflation and jobs and you get a rough fair value for the policy rate, then compare it to what the market is pricing to spot where the mispricing sits.

How the Fed signals its reaction function

The Fed does not leave the market to guess. It broadcasts the function through three channels. Forward guidance is the language in the statement and the press conference that tells you the conditions under which policy will move, the if-then of the reaction function spelled out in words. Listen for whether the committee is data-dependent, patient, or in a hurry.

The dot plot is the second channel. Four times a year each policymaker marks where they expect the policy rate to sit at year-end and beyond. The dots are not a promise and they shift meeting to meeting, but the median dot and the spread around it tell you the committee’s central view and how divided it is. A hawkish shift in the dots can tighten financial conditions on its own, before a single rate has moved.

Speeches and testimony fill the gaps between meetings. Individual policymakers test arguments and signal where the debate is heading, and the chair’s word carries the most weight because the chair shapes the consensus. Read all three together and you are reading the reaction function in real time, which is the edge the data alone will never give you.

Why traders model the function, not just the data

Here is the desk discipline. Before any major release, write down what you think the Fed does in each scenario: hot print, in-line, soft. That is your reaction function. When the number lands, you already know the policy implication and you are trading the gap between your function and what the market had priced, not scrambling to interpret a headline live.

This is why two identical data prints can move the dollar in opposite directions. The same hot CPI is dollar-bullish when the Fed is fighting inflation and barely registers when the Fed has already declared victory and shifted to the jobs side of the mandate. The print is constant; the function is what changed. Model the function and you stop being surprised by price action that looks irrational on the data alone, and you start positioning for the repricing before it happens.

The current hawkish skew into Warsh’s first FOMC

Right now the reaction function is skewing hawkish, and you can see why from both mandates. The labour market has come in hot, with payrolls and wages running firmer than a Fed trying to ease would like. A hot jobs market keeps the maximum-employment dial close to goal and removes the cover the Fed would need to cut, so the function leans towards holding or even tilting tighter.

On the price side, the conflict in the Middle East and the strikes on Iran put an upside skew on the inflation path through energy. War-driven oil is exactly the kind of supply shock that lifts headline inflation and, more dangerously, threatens to lift inflation expectations if it lingers. A Fed that has spent years defending its credibility will not look through that risk lightly.

Layer on Kevin Warsh chairing his first meeting. Warsh carries a hawkish reputation and a known scepticism of running policy too loose for too long, which markets read as a reaction function with a lower tolerance for inflation surprises. Put the three together, hot jobs, a war-driven inflation skew and a hawkish new chair, and the desk’s base case is a reaction function tilted away from cuts. That is dollar-supportive and tends to firm the front end of the curve until something on the jobs side cracks. Watch the dots and the chair’s tone at the meeting for confirmation, because that is where the function gets repriced.

Frequently asked questions

What is the Fed’s reaction function?

It is the predictable way the Federal Reserve responds to the economy when setting interest rates. In short, inflation above target pushes policy tighter and a weak labour market pushes it easier. It maps incoming data onto rate decisions, so if you know the function you can anticipate how the Fed reacts to any given print.

What is the dual mandate?

The dual mandate is the Fed’s two legal goals: stable prices and maximum employment. Price stability is anchored on a 2 percent inflation target measured on core PCE. Maximum employment is the highest sustainable level of jobs. When the two goals conflict, the Fed weighs which is further from target, and that trade-off drives the reaction function.

What is the Taylor rule?

The Taylor rule is a simple formula for a reaction function. It says the policy rate should equal a neutral rate plus a response to inflation above target plus a response to the employment or output gap. Crucially it raises rates more than one for one with inflation so real rates rise. The Fed does not follow it mechanically but uses its intuition.

Why does the reaction function matter for the dollar?

Because the dollar moves on data relative to expected policy, not data alone. The same hot inflation print lifts the dollar when the Fed is fighting inflation and barely moves it when the Fed has shifted to the jobs side. Model the function and you can call the dollar’s direction from a release before the market finishes repricing.

What is the dot plot?

The dot plot is a chart, published four times a year, where each Fed policymaker marks where they expect the policy rate to sit at year-end and beyond. The median dot shows the committee’s central view and the spread shows how divided it is. It is a signal, not a promise, but a hawkish shift can tighten conditions on its own.

Why is the Fed’s reaction function hawkish into Warsh’s first FOMC?

Three things stack up. The labour market has run hot, which removes the cover the Fed needs to cut. The conflict with Iran skews the inflation path higher through energy. And Kevin Warsh, chairing his first meeting, carries a hawkish reputation and low tolerance for inflation surprises. Together they tilt the function away from cuts, which tends to support the dollar.

For general information and education only, not financial advice. Markets move quickly and trading is leveraged, most retail accounts lose money. KenMacro has commercial partnerships with brokers and may earn commission at no extra cost to you.