U.S. CPI Methods Changed Housing and Price Measurements Over Decades

U.S. consumer inflation measures changed across several decades, altering how the index counts housing and consumer purchases, with differing effects that matter when readers interpret CPI readings.

Rental equivalence treats owner-occupied housing as a shelter service rather than measuring it primarily through home prices. The CPI-U began using the method in 1983, and the CPI-W followed in 1985. When introduced, it increased the rate of change in the shelter index.

A sampling correction for food items took effect in January 1995 and expanded to all categories in June 1996. Initial estimates put the reduction in overall CPI growth at 0.11% for the food adjustment, with a further 0.10% reduction from the broader change. The revisions addressed identified upward measurement bias.

In January 1999, the CPI began using a geometric mean formula in many categories to reflect consumers substituting among items within basic categories. The listed changes did not all move measured inflation in the same direction: rental equivalence initially raised shelter-index growth, while the food sampling changes lowered estimates of overall CPI growth. The record does not show a demonstrated long-run tendency for CPI methodology as a whole to produce lower inflation than alternatives.

The latest September 2026 CPI reading rose 0.6% from August and 3.7% from a year earlier. The data were released Oct. 14 at 8:30 a.m. ET (12:30 UTC). The September CPI report included the latest inflation figures.