How to read an average price

An average price is published for a narrowly described product, not for a whole aisle. The egg figure, for example, covers a dozen large grade A eggs. A carton of extra-large or organic eggs is a different product with a different price, and it is not in that number.

Every price page on this site quotes the official description, so you can see exactly what is being measured before you compare it with what you buy.

The figure combines prices collected in many cities. No single store charges exactly this amount, and prices in your area can sit well above or below it. Treat it as a yardstick for the country, not as a quote for your neighborhood.

These prices are not seasonally adjusted. If something usually costs more at one time of year, the published figure rises then too. That is why a price page compares the latest month with the same month a year earlier as well as with the month before: the year-over-year change is not thrown off by the calendar.

A month's figure is published some weeks after the month ends, so the latest price on a page describes a month that is already over. Each page names that month.

Occasionally a month is not published. When that happens the page shows a gap in the chart and says so in the table. Nothing is estimated to fill it.

An average price is a dollar amount for one item. An inflation rate describes how the cost of a broad basket of goods and services has changed. One item can get cheaper while the basket as a whole gets more expensive, so a falling price for eggs or gasoline says little about prices in general.

Compare it with your own receipt for the same kind of product, and watch the direction rather than the cents. If you pay much more than the average, the difference is usually the product (a different size, grade or brand) or the place, and the price pages show whether the national figure has been rising or falling.