The Federal Communications Commission's rules governing media ownership, traditionally implemented under a trustee model, have changed radically as the result of deregulatory moves in the 1980's and a change to a regulatory implementation based on economic competition in the mid 1990's. Under the statutory obligation of Statute 202 to review ownership rules, the FCC has acted outside of the guidelines of the rulemaking procedures of the Administrative Procedure Act, and the Third Circuit Court of Appeals has remanded a pair of FCC decisions to the agency for lack of supporting evidence. A significant part of the evidence issue lies in the reality that at the heart of the regulation of media ownership is an empirically unexplored relationship between the diversity of content and ownership. The belief that each owner represents one viewpoint has been used by the FCC as a proxy measurement when assessing the changes on the quantity and quality of the informational content being provided to local audiences by broadcasters. This dissertation explores the history of the ownership-diversity relationship, beginning with the FCC's 1975 ban on Newspaper-Broadcast Cross-Ownership, and tracks the development of media ownership policy through the changes to the broadcast industry which began after the passage of the 1996 Telecommunications Act. 1039 individual decisions on media ownership were analyzed for evidence that the agency had assessed the effects of ownership on viewpoint diversity. This analysis demonstrates that there is a minimal amount evidence of which exists to support the central theory at the heart of the FCC's media ownership policy. After discussing the evidence the FCC continues to collect as part of the ongoing 2010 Quadraennial review, the author concludes that the lack of supporting evidence is not a new problem, nor has the agency taken the necessary steps to evaluate the effects of policy implementation.