Why typical is not the same as average

Here is a made-up example to show the arithmetic. Five shops sell the same thing for $2, $2, $3, $3 and $10.

The average is (2 + 2 + 3 + 3 + 10) ÷ 5 = $4. Yet four of the five shops charge $3 or less. The one expensive shop has pulled the average above what almost everyone pays.

Line the same five prices up in order and take the one in the middle: $3. That is the median. Half the shops charge that or less, half charge that or more. Change the $10 to $100 and the average jumps to $22, but the median is still $3.

A single number hides how spread out prices are, so this site also shows the middle half: the range that is left when you set aside the lowest quarter and the highest quarter. In the example that range runs from $2 to $3. A price inside it is ordinary. A price outside it is unusually low or unusually high.

On a page, that range is the highlighted band, the median is the dark line inside it, and every tick is one place or one month. You can see at a glance where a figure sits among the rest.

If prices are spread evenly, with no extreme values, the average and the median land close together and either one will do. They part ways when a few values are far from the rest, which is common with costs: most are bunched together and a handful are much higher.

Check whether the figure you care about falls inside the highlighted band. If it does, there is nothing unusual about it. If it falls outside, it is worth asking why. The methodology page explains how the band is worked out.