From zero
06 From zero · Traditional markets · United States

CPI: why the same money buys less

“Inflation fell, but prices are still high.” That sentence looks like a contradiction and isn't — it is the difference between speed and height, and it is the commonest misunderstanding in all of economics.

Fêr UlianovOpening · 15 s · in Portuguese

The sentence
CPI slowed to 2.9% over twelve months, and core rose 0.3% on the month — but prices are still higher than a year ago.

Blurred on purpose. It holds four numbers and three different meanings.

The idea

Inflation is the speed, not the height

Inflation is how much prices rise per unit of time. It is a speed. The price itself — what the shopping basket costs — is the height. Two different quantities, and the paper quotes both in one sentence without warning you.

The whole confusion comes from that. When the news says inflation fell, it is not saying anything got cheaper. It is saying prices are still rising, only more slowly. For prices to actually fall, inflation would have to go negative — and that has another name.

The price of the same basket
Inflation, per year
Cost
In three years

Three years, three scenarios, the same basket. Notice the top line only falls in the third. In the other two it rises — and in the first it rises while inflation falls. Illustrative scenarios.
The index

The CPI is a basket, not a price

The CPI is published monthly by the Bureau of Labor Statistics. It does not track a price: it tracks a basket of goods and services, and each item's weight comes from surveys in which thousands of households record what they actually bought.

So the number in the paper is the inflation of an average family that does not exist. Your basket is a different one: somebody paying rent in an expensive city and somebody with the house paid off who drives 200 km a week live through different inflations in the same month, with the same prices.

weight rise this year
Housing+4.0%
Transport+1.0%
Food+2.5%
Health+3.5%
Other+2.0%
Index inflation
This basket's inflation
The same prices rising the same way, and three different inflations — because what changes is each item's weight in the budget. Illustrative weights and rises, kept round so the arithmetic stays visible.
The core

Core is the same index without food and energy. Not because food and fuel don't matter — they matter enormously. Because they swing too much: a drought or a war moves the month's number and says nothing about the trend. Core is an attempt to see the bottom, not to deny the surface.

The two numbers

Monthly and twelve-month are not the same thing

Every inflation story carries two numbers, and they measure different things. The monthly one is what happened in that month. The twelve-month one compares with the same month a year earlier, which is why it moves slowly: for it to fall, the new month has to come in below the month dropping out, twelve months back.

And the monthly number deceives by its size. A figure that looks tiny, repeated twelve times, becomes something else. Drag it and see.

Change on the month
If it repeated for twelve months
The basket doubles in price in
This is why 0.3% in a month is not good news: repeated, it is nearly 4% a year. And it is why the rate-setting committee looks at the whole series, not at one month.
The detail almost nobody knows

The Fed's target is not measured by the CPI

Last lesson said the Fed aims at 2% inflation. But its target is not about the CPI: it is about a different index, the PCE, produced by a different agency with a different weighting formula.

Both measure inflation and usually tell similar stories, but they do not give the same number. It is worth knowing for one practical reason: when a story says “above the Fed's target” right after quoting the CPI, it is comparing two different indices — and almost never says so.

The proof

Now read the sentence

It's the same one from the top, unblurred. Tap each highlighted part.

to , and rose — but prices are still .
Start here

Five pieces

Each highlighted part measures something different. Tap one.

Five taps and the sentence is done.

You can already answer these

If this landed, the lesson did what it promised

  • Inflation is speed; price is height. Falling inflation is still rising prices.
  • Prices only truly fall with negative inflation — and that is called deflation.
  • The CPI is an average family's basket; your basket has different weights.
  • The monthly number and the twelve-month number measure different things.

Fêr UlianovClosing · 32 s · in Portuguese

Educational material. The scenarios, the basket weights and the per-category rises are illustrative, kept round so the arithmetic stays visible — none is a published figure, and the sentence at the top is an anatomy, not a real news story. What is structural — who publishes, what core is, how the basket is built — comes from official methodology. It is not a recommendation to buy or sell.