Inflation, explained simply — and what actually causes it

If you've ever stared at a receipt and thought "I swear this used to be cheaper," you've already done the harder half of understanding inflation. The receipt is real. The question is why the number on it keeps creeping up.

This post is a from-scratch explainer. No jargon for its own sake. Just what inflation is, what causes it, and which of those causes are actually doing the heavy lifting right now.

What "inflation" actually is

Inflation is a sustained, broad rise in prices over time. Two words there matter:

• Sustained — not a one-off jump. Eggs spiking because of bird flu isn't inflation by itself; it's one product moving. Inflation is when the average price of stuff in a typical household basket goes up and stays up.
• Broad — across many goods and services, not just one or two. The government measures it with a basket of ~80,000 specific prices (the Consumer Price Index, or CPI), weighted by how much typical households actually spend on each item.

The cleanest way to think about it: inflation is the dollar losing buying power. A dollar in 2019 bought ~0.71 dozen eggs. Today it buys ~0.31 dozen. The egg hasn't changed. The dollar has.

This is also why "the cause of inflation" is a slippery question. You can blame the price (something pushed it up) or you can blame the dollar (something made it worth less). Most real-world inflation is a mix of both — and serious economists spend their careers arguing about the ratio.

The five honest causes

There are really only five mechanisms that move prices up in a sustained, broad way. Every "cause of inflation" you'll read about is one of these — or some combination.

1. Demand-pull — too many dollars chasing too few goods

The textbook one. When buyers want more of something than the economy can produce at current prices, prices rise to ration the available supply.

A simple version: imagine a town with 100 loaves of bread for sale each morning and 100 people who want one. Price settles wherever clears the market. Now drop $500 in stimulus checks onto every person, and suddenly 150 people want bread. There are still only 100 loaves. The price goes up until 50 people decide it's not worth it anymore.

Real-world demand-pull rarely looks that clean, but the mechanism shows up whenever:

• Disposable income jumps (tax cuts, stimulus, wage gains).
• Borrowing gets cheap (low interest rates, easy credit).
• A previously suppressed buying urge releases (post-pandemic travel demand was a textbook case).

Demand-pull is the dominant story politicians tell when they didn't cause it and the opposing story when they did.

2. Cost-push — making and shipping stuff got more expensive

Prices also rise when the inputs producers buy — raw materials, energy, labor, shipping — get more expensive. Producers either eat the cost (and their profits shrink), pass it along (and prices rise), or some mix.

Cost-push is what happened to bread in 2022. Wheat futures spiked when Ukraine's harvest was disrupted by the Russian invasion. Diesel for trucks got more expensive because oil markets were chaotic. Bakeries faced a wage bill that had risen meaningfully in the prior year. Add it all up, and white bread at the store crossed two bucks a pound — a number it had spent most of the prior decade well below.

Cost-push is the dominant story producers tell when they raise prices, and the dominant story buyers don't trust because producers also raise prices when they think they can get away with it.

3. Supply shocks — something broke

Closely related to cost-push, but worth separating because it shows up differently in the data. A supply shock is a sudden contraction in the available quantity of something — not because it got more expensive to make, but because less of it exists or can move.

Examples from the last few years:

• Bird flu (HPAI) in 2022 and 2024-25. Roughly 100 million U.S. layer hens were culled to stop the spread. That's not a small dent — that's a significant share of the country's egg-laying capacity, gone in weeks. Eggs went from ~$1.40 in 2019 to a peak well above $4 a dozen.
• Drought-driven cattle herd shrinkage. U.S. cattle herds in 2024-25 sat near their lowest levels since the 1950s. Ground beef prices reflect that math: when there are fewer animals, the meat from them costs more per pound.
• Pandemic supply chains. Ports clogged, factories shut, freight rates spiked 5x. Anything that moved by container — which is most consumer goods — got more expensive almost overnight.

Supply shocks are usually the most visible cause to consumers because they're concentrated in specific items. The shock to bread isn't the same as the shock to eggs, even when both are happening at once.

4. Monetary expansion — more dollars in the system

The dollar's value is determined by, among other things, how many of them are floating around relative to the goods they can buy. When the central bank (the Federal Reserve) expands the money supply faster than the economy expands its capacity to produce, each dollar buys less.

The Fed expanded the money supply massively in 2020-21 to keep the financial system functioning during COVID. The M2 measure of money supply grew about 40% in two years. Some economists argue this was the dominant driver of the 2022 inflation peak; others argue it was a secondary factor next to supply shocks. The truthful answer is "both mattered, the ratio is debatable, and reasonable people disagree."

What's not debatable: when there are far more dollars chasing roughly the same goods, the dollar buys less. That's just arithmetic.

5. Expectations — believing prices will rise makes them rise

This is the spookiest one because it sounds circular but is real. If workers expect prices to rise 4% next year, they'll ask for 4% raises. If businesses expect their input costs to rise 4%, they'll set their prices 4% higher in advance. If everyone acts like inflation will be 4%, inflation will end up close to 4% — regardless of what's actually happening in the underlying economy.

This is why central banks talk about "anchoring expectations" obsessively. Once people stop believing the central bank will get inflation back down, getting it back down becomes much harder. The U.S. had a textbook version of this in the 1970s, and breaking it required Fed Chair Paul Volcker pushing interest rates above 19% and triggering a brutal recession.

So which one is doing the work right now?

The 2021-2023 inflation surge was unusual because all five mechanisms fired at roughly the same time. Stimulus pumped demand. Supply chains snapped. Energy markets convulsed. Money supply ballooned. And after eighteen months of headlines screaming about it, expectations started to drift.

That's why it ran so hot. And it's also why bringing it down has been slow — each mechanism cools on its own clock. Supply chains have healed. Money supply has tightened. Expectations have re-anchored. But cost-push pressures (especially in food and energy) haven't fully unwound, and demand stayed sturdier than the Fed wanted for longer than it expected.

If you want a single sentence: the 2022 peak was supply-side, the 2023-2024 stickiness was demand-side, and the boring everyday inflation underneath both is monetary.

What this means for your receipt

A few things follow from all of this:

Different items have different stories. Eggs are mostly bird flu. Gas is mostly oil markets and refining capacity. Electricity is mostly state-level grid math. Treating "inflation" as one thing is how people end up shouting past each other. Look at the specific item.

"Greedflation" is real but smaller than headlines suggest. Some companies absolutely used the cover of broad inflation to raise prices more than their costs justified, then kept those margins after costs eased. The data shows this clearly in some sectors (notably consumer staples) and barely at all in others. It's a contributing factor, not the whole story.

Wages matter, but slowly. If wages rise at the same pace as prices, you break even in real terms. The honest answer for most of the last five years is that wages lagged prices for about two years, then caught up roughly. Whether your household experienced that depends heavily on industry, region, and timing.

There's no single villain. Anyone telling you inflation was caused by one thing — and pointing at it confidently — is selling you something. Usually a political story. The reality is that five different mechanisms fired together, in proportions that economists will still be arguing about in fifty years.

What you can do is stop trying to win the argument about who caused it, and start looking at which specific prices in your basket actually moved — and which moves are still worth making about them.

That's what the rest of this site is for.