What is inflation, actually?

Inflation is a general rise in prices across the economy, which is the same thing as each dollar buying a little less. The US measures it mainly through the Consumer Price Index, a monthly survey of what a representative basket of goods and services costs.

Some inflation is normal and intended. The Federal Reserve targets about 2 percent a year, on the theory that mild inflation keeps the economy moving while deflation, falling prices, tends to stall it. The pain comes when inflation runs hot and wages lag behind it.

One trap in how people experience it: when inflation slows, prices do not fall back. Disinflation means prices rise more slowly, not that the grocery bill returns to what it was. That gap between the statistic and the receipt is why the topic makes everyone angry.