How the BLS Builds the CPI The CPI is not a rough estimate but a carefully built, survey-driven system refined over more than a century. To construct it, the BLS gathers price data on hundreds of everyday goods and services, known as the “market basket.” This effort spans roughly 8,000 housing units and 23,000 retailers, service providers, and online outlets across 75 urban areas nationwide, creating a detailed snapshot of how prices move in the real world. Approximately two-thirds of that price collection is done by personal visits from CPI data collectors to brick-and-mortar stores. The remaining data are collected by telephone or on outlet websites and apps. This is painstaking, … [Read more...]