The short version
- Demand-pull inflation is too much spending chasing the available goods.
- Cost-push inflation starts with supply: energy, shipping, a failed harvest.
- Expectations are self-fulfilling, which is why central banks guard them so carefully.
- The Fed's tools work on demand; they do nothing about a supply shock directly.
Three mechanisms, not one
Inflation is a general rise in prices across an economy. Asking what causes it is a bit like asking what causes a fever: there are several mechanisms, they can run at once, and the treatment depends on which one you are looking at.
1. Demand pulls prices up
More money chasing the same quantity of goods. Households and businesses want to buy more than the economy can currently produce, so sellers raise prices rather than run out of stock.
Demand can rise for ordinary reasons — rising employment and incomes, cheap credit, government spending, savings accumulated and then released. This is the kind of inflation a central bank can genuinely do something about, because raising interest rates makes borrowing costlier and saving more attractive, which cools spending.
The tell is breadth. When demand is the driver, prices rise across most categories at once, and the labour market is usually tight.
2. Supply pushes prices up
The other direction. The quantity available falls, or the cost of producing it rises, and prices rise even though demand has not moved.
Oil is the classic example: energy enters the cost of almost everything, so a supply shock propagates through the whole price level. Others are a failed harvest, a shipping disruption, a factory closure, a tariff, or a war.
This kind is genuinely awkward for a central bank. Raising rates does not produce more oil. It can only reduce demand until it matches the smaller supply — which means deliberately slowing the economy to bring prices down, at a cost in jobs. Central banks generally try to “look through” a supply shock they expect to fade, and respond only if it starts feeding into wages and expectations.
The tell is concentration. When supply is the driver, the rise is sharp in particular categories rather than broad.
3. Expectations make it stick
This is the mechanism people underrate, and it is why central banks talk so much about credibility.
If everyone expects 5 percent inflation next year, they act on it now. Workers ask for 5 percent raises. Firms build 5 percent into next year’s prices and into contracts. Lenders demand it in interest rates. Those actions produce the 5 percent, whatever started the process.
The reverse holds too. If people are confident inflation will return to about 2 percent, they do not chase it, and a supply shock passes through once and fades. This is the entire argument for a central bank having an explicit, publicly stated target and defending it: the target is not just a goal, it is a coordination device for everyone else’s expectations.
Expectations becoming “unanchored” is the outcome central banks fear most, because recovering them historically requires a deep recession.
Where the money supply fits
You will hear that inflation is “always and everywhere a monetary phenomenon”. Over long horizons and large magnitudes, the relationship between money growth and inflation is real and well documented — sustained high inflation has never happened without accommodative money.
Over short horizons it is a much looser guide. How fast money circulates varies, and money created that sits in reserves rather than being spent does not bid up the price of anything. It is better understood as a description of the demand channel over years than as a month-to-month predictor.
Why the diagnosis decides the response
| Driver | What it looks like | What the Fed can do |
|---|---|---|
| Demand | Broad-based, tight labour market | Raise rates; this is what the tool is for |
| Supply | Concentrated in energy, food, specific goods | Little directly; look through it unless expectations move |
| Expectations | Wages and prices rising together, forecasts drifting | Defend the target loudly and act early |
This is why the Fed watches core inflation — the measure excluding food and energy — alongside the headline. Not because food and energy do not matter to households, obviously they do, but because stripping out the most supply-driven categories gives a clearer read on whether the rise is broad. The inflation rate page carries the current figure with its “as of” date.
How to read the coverage
- “Inflation is caused by X” — usually one of the three, stated as if it were the whole story. Ask whether the rise is broad or concentrated.
- “The Fed is fighting inflation” — it is reducing demand. That works on the first mechanism and only indirectly on the second.
- “Wages are causing inflation” — wages rising with productivity are not inflationary. Wages rising faster than productivity, across the economy, are part of the expectations mechanism.
- “Inflation is falling” — prices are still rising, more slowly. See the glossary term for that distinction, which is the one most commonly muddled.
Sources
- 1.Board of Governors of the Federal Reserve System, Why does the Federal Reserve aim for inflation of 2 percent over the longer run?. Retrieved Sep 5, 2026.
- 2.U.S. Bureau of Labor Statistics, Consumer Price Index. Retrieved Sep 5, 2026.
- 3.Board of Governors of the Federal Reserve System, Monetary Policy: What Are Its Goals?. Retrieved Sep 5, 2026.
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