Relative Index Number

A relative index number (or price relative) measures the price change of a single commodity between the base period and the current period, expressed as a percentage:

where $p_0$ is the price in the base period and $p_1$ is the price in the current period. Relative index numbers are the building block for the group-level methods that follow — when several commodities need to be tracked together instead of just one, those relatives are co …