Consumer Price Index:

(CPI) in any year is the cost in that year of a bundle of goods and services purchased by a typical urban consumer compared to the cost of that bundle of goods and services in a base period. A narrow measure of inflation, because confined to consumer goods and services.

For this series, the base period is the 1982-84 annual average. The series used in MeasuringWorth extends the United States Bureau of Labor Statistics CPI-U (consumer price index for all urban consumers) series back in time. The official CPI series begins in 1913, but improvements to the official series are made here, so the CPI series here is identical to the BLS series only from 1978 onward.

For further discussion of the limitations of the CPI, and for detailed exposition of development of this CPI series, please read What Was the Consumer Price Index Then? A Data Study.