In today's economy, Big Data is big business. Data brokers-companies that collect consumers' personal information and resell or share that information with others-are important participants in this Big Data economy. In this report, the Federal Trade Commission ("FTC" or "Commission") discusses the results of an indepth study of nine data brokers. These data brokers collect personal information about consumers from a wide range of sources and provide it for a variety of purposes, including verifying an individual's identity, marketing products, and detecting fraud. Because these companies generally never interact with consumers, consumers are often unaware of their existence, much less the variety of practices in which they engage. By reporting on the data collection and use practices of these nine data brokers, which represent a cross-section of the industry, this report attempts to shed light on the data broker industry and its practices.