The U.S. Consumer Price Index (CPI), the major measure of retail price change, has enormous consequences for economic policy and federal programs. Most critically, the index affects hundreds of billions of dollars in the federal budget by defining the "cost of living" adjustments that are automatically applied to everything from social security payments to tax brackets. Yet the CPI has also been very controversial, and economists continue to debate its accuracy. In this book Stapleford interweaves economic theory with political history to explain why Americans came to vest so much authority in measurements of the "cost of living," despite their inevitable ambiguities. By exploring the context and consequences of methodological decisions, he shows how a critical history of these statistics can enrich our understanding of labor history, economic policy, and the American welfare state.