The Retail Price Index (RPI) is an official index used to measure changes in the prices of goods and services purchased by consumers. It serves a number of important purposes in the business world, including helping businesses monitor their costs of production, setting inflation rates for wages, and providing key data points for contract negotiations. Used in procurement, the RPI can be used to set benchmark values for negotiating contracts, allowing suppliers and purchasers to compare prices over time and ensure they are getting a fair deal.