Why Some Inflation Responds to Interest Rates and Some Doesn't

A country that spent thirty years failing to generate inflation just recorded a meaningful rise in consumer prices. It did not do so by fixing its own economy. The inflation arrived from somewhere else.

Not all inflation is the same thing

Inflation is usually discussed as a single quantity that goes up or down, and central banks are described as raising rates to bring it back. That description works well enough most of the time, and it breaks in exactly the situations that matter most.

The reason is that inflation has different origins, and the origin determines whether interest rates can do anything about it.

Broadly there are two kinds. Domestic inflation comes from within an economy — demand exceeding supply, wages rising faster than productivity, credit expanding. Imported inflation comes from outside — a commodity the country buys becoming more expensive, or its currency weakening so that everything bought abroad costs more in local terms.

They look identical in the headline figure. They behave nothing alike.

Why interest rates work on one and not the other

Raising interest rates works by suppressing demand. Borrowing becomes more expensive, so households postpone purchases and firms postpone investment. Demand falls, and prices follow.

That is a coherent mechanism when the problem is demand. Too much money chasing too few goods, and the central bank removes some of the money.

It is close to useless when the problem is supply. If a conflict has restricted the flow of oil, raising domestic interest rates does not produce more oil. It reduces economic activity without addressing the shortage — which is why the textbook description of tightening into a supply shock is that you get the recession without the disinflation.

This is the central difficulty in every energy-driven inflation episode, and it is why central bank committees fracture during them. The disagreement is not usually about the data. It is about whether the tool applies at all.

The currency channel

Interest rates do not only affect domestic demand. They also affect the exchange rate — and for imported inflation, that turns out to be the more important mechanism.

Capital tends to flow toward higher yields. When a central bank raises rates, or is expected to, its currency typically strengthens as investors move money in to capture the return. A stronger currency means imports become cheaper in local terms.

So a country facing inflation driven by expensive imports does have a lever after all — not by reducing demand for oil, but by making each barrel cost less in its own currency.

This is why the same policy can be effective in one economy and futile in another. A large, relatively closed economy that produces much of what it consumes gets little from the currency channel. A smaller, import-dependent economy with a weak currency gets a great deal from it.

The clearest case study available

Japan spent roughly three decades attempting to generate inflation and largely failing. Rates were held at or below zero for years. Asset purchases were enormous by any historical standard. Domestic price growth stayed stubbornly absent.

Then inflation arrived without being summoned — through energy costs and a weak currency, rather than through domestic demand finally recovering.

That produces an unusual policy situation. The inflation is imported, so the demand channel is largely irrelevant. But the currency channel is highly relevant, because a persistently weak currency is amplifying every imported price. Raising rates would strengthen the currency, and a stronger currency directly reduces the cost of the energy that is causing the problem.

For an import-dependent economy with a weak currency, tightening can genuinely address supply-driven inflation — not by fixing supply, but by changing what that supply costs at home.

How to read this in practice

• Ask where the inflation came from before assuming what happens next. Domestic and imported inflation produce different policy responses to the same number.

• Watch the currency alongside the inflation print. For import-dependent economies, the exchange rate is doing much of the work.

• Expect committee disagreement during supply shocks. It reflects a genuine question about whether the tool applies, not incompetence.

• Be careful comparing across countries. The same inflation rate means different things in a large closed economy and a small open one.

• Remember the core measure excludes energy. In an imported-inflation episode, the headline figure and the targeted figure can diverge for a long time.

The point

Inflation is a single word covering at least two distinct phenomena with different causes, different dynamics and different remedies.

The headline number tells you the temperature. It does not tell you the source of the heat — and the source determines whether the thermostat is connected to anything.