The American Customer Satisfaction Index (ACSI) is a national economic indicator of customer evaluations of the quality of products and services available to household consumers in the United States. The ACSI uses data from interviews with roughly 70,000 customers annually as inputs to an econometric model for measuring customer satisfaction with more than 225 companies in 47 industries and 10 economic sectors, as well as over 100 services, programs, and websites of federal government agencies. ACSI results are released on a monthly basis, with all measures reported using a scale of 0 to 100. ACSI data have proven to be strongly related to a number of essential indicators of micro and macroeconomic performance. For example, firms with higher levels of customer satisfaction tend to have higher earnings and stock returns relative to competitors. Stock portfolios based on companies that show strong performance in ACSI deliver excess returns in up markets as well as down markets. And, at the macro level, customer satisfaction has been shown to be predictive of both consumer spending and gross domestic product growth. The Index was founded at the University of Michigan’s Ross School of Business and is produced by ACSI LLC.