Inflation gets reported as a single number, 3.7% for the US in September, as if every price in the country rose by the same amount. In reality the spread was enormous. Gasoline cost 34% more than a year earlier, while used cars got cheaper and car insurance fell 5%. Understanding how inflation works means looking at the parts underneath that headline, because they often move in opposite directions and say very different things about where prices and interest rates go next.
Quick answer: Inflation is the overall rise in prices across an economy, measured in the US by the Consumer Price Index. CPI is made up of hundreds of categories, each weighted by how much households spend on it. Goods, services, housing, energy and wages all behave differently, which is why economists and central banks look at the components as closely as the headline.
Know When the Next Inflation Data Lands
The economic calendar lists every CPI, wage and producer price release with its expected impact, so you can see what’s coming before it moves markets.
What CPI Measures
The Consumer Price Index tracks the prices of a basket of goods and services that typical urban households buy, including groceries, rent, haircuts and airfares. The US Bureau of Labor Statistics gives each category a weight, called its relative importance, based on how much of the average household budget it takes up.
| Component | Share of the basket | Price change, 12 months to September 2026 |
|---|---|---|
| Shelter | 35.3% | +3.2% |
| Food | 13.5% | +2.5% |
| Goods other than food and energy | 18.8% | +0.7% |
| Energy | 7.4% | +20.4% |
| All items | 100% | +3.7% |
Figures from the BLS Consumer Price Index, September 2026.
A category with a big weight and a small rise can add as much to inflation as one with a small weight and a huge rise. Multiply the two together and energy’s 20.4% rise added roughly 1.5 percentage points to the headline, while shelter’s 3.2% rise added about 1.1.
How Inflation Works in Each Part of the Basket
Energy
Energy makes up only around 7% of the basket, but it can swing by 20% or more in a year, which gives it an outsized effect on the headline. In September it accounted for more than half of the monthly rise in CPI. Our article on oil prices and inflation shows how energy costs spread into other prices over time.
Goods
Goods like cars, clothes, furniture and electronics depend heavily on global supply chains and the strength of the dollar. They were rising just 0.7% a year in September, and some were falling.
- Used cars and trucks: down 1.5%
- New vehicles: up 0.6%
- Apparel: up 3.4%
Services
Services cover medical care, haircuts, restaurant meals, car repairs and a long list of other things people pay someone else to do. Most of their cost is labor, which means services inflation tends to follow wages more closely than oil prices. The clearest example sits in the food figures. Groceries rose 1.8% over the year, while meals out rose 3.5%, because a restaurant bill pays for the cook and the server as well as the ingredients.
Housing
Shelter is the single biggest part of CPI, at more than a third of the basket. Most of it is owners’ equivalent rent, an estimate of what homeowners would pay to rent their own home. It’s based on surveys of rents and tends to lag changes in the market by many months, which is why housing inflation can keep rising after new rental prices have already cooled.
Wages
Wages sit outside CPI and still shape it heavily. US average hourly earnings rose 3.0% over the year to September, while prices rose 3.7%, leaving real wages down 0.7%. Falling real wages squeeze spending, and if workers push for bigger raises to catch up, labor-heavy services can stay expensive for longer.
Core Inflation
Core CPI strips out food and energy, the two most volatile parts, and rose 2.6% over the year to September. It gives a steadier read on the underlying trend, and our inflation watch on the next CPI report explains why markets are watching it closely this fall.
Why Inflation Components Point in Different Directions
Different parts of the basket respond to different forces, often at different speeds.
| Force | Parts it affects most | Speed |
|---|---|---|
| Oil and gas prices | Energy, airfares, delivery costs | Days to months |
| Supply chains and the dollar | Cars, electronics, clothing | Months |
| Wages | Restaurants, medical care, personal services | Months to years |
| Rents | Shelter | A year or more |
That’s how September’s report can show gasoline up by a third while used car prices fall. A supply shock in energy and a slowdown in demand for big purchases can happen at the same time, and the headline averages them together.
What Central Banks Look at
Central banks care most about the parts of inflation that are slow to fall. The Fed’s own 2% goal is set for the PCE price index, a measure similar to CPI with different weights, and policymakers pay close attention to services excluding housing, sometimes called supercore inflation, because it tracks wage pressure closely.
When energy alone pushes inflation up, central banks often wait to see if it fades. When services and core inflation climb too, they’re more likely to raise rates. Our article on what makes inflation sticky looks at that second kind in more detail.
What the Inflation Mix Means for Markets
- Forex: a rise in core or services inflation tends to lift expectations of higher US rates, which can support the dollar, and the forex page covers how rate expectations move currency pairs
- Bonds: persistent inflation pushes yields higher as investors demand more compensation
- Stocks: companies with pricing power can pass rising costs on, while businesses facing higher wages and slower sales can see margins squeezed
- Metals: gold often draws interest when inflation looks hard to control, though higher yields can work against it
Frequently Asked Questions
What are the main components of CPI?
The main components of CPI are shelter, food, energy, goods and services. Shelter is the largest at about 35% of the basket, followed by goods other than food and energy at about 19% and food at about 13.5%. Energy is only around 7% of the basket, but its prices swing much more than the others.
Why is housing such a big part of CPI?
Housing is a big part of CPI because it’s the largest single expense for most households. The US index measures it mainly through rent and owners’ equivalent rent, an estimate of what homeowners would pay to rent their own home. Shelter makes up about 35% of the basket and changes slowly, so it strongly shapes the trend.
How do wages affect inflation?
Wages affect inflation mainly through services, where labor is the biggest cost. When wages rise faster than productivity, businesses like restaurants, clinics and repair shops tend to raise their prices. In September 2026, US average hourly earnings rose 3.0% over the year, slower than inflation, which left real wages down 0.7%.
What is supercore inflation?
Supercore inflation measures the price of services excluding energy and housing. Economists watch it because it’s closely linked to wages and tends to move slowly, which makes it a useful guide to underlying inflation pressure. Central banks pay attention to it when deciding if inflation is likely to stay high without energy shocks.
