In this paper we outline a key mechanism through which organizational fields are constituted. We suggest that in competitive fields, the market serves as a magnet around which groups of actors consolidate, and that cognition of markets occurs through the creation, distribution, and interpretation of a web of information about the “market.” To illustrate our theory, we present a case study of the Billboard music chart from the commercial music industry to show that changes in either scope, methodology, or political tone with which market information is presented can provide a major jolt to the participants' understanding of their field.