ownership concentration poses harm to competition or to consumers is precisely the ques- tion upon which the antitrust laws and their enforcers focus The modern approach to analysis of ownership concentration is illustrated by the frame work set out in the DOJ/FTC Merger Guidelines(Merger Guidelines or Guidelines). The Guidelines, while certainly not infallible, are widely respected by courts and commenta- tors alike. The guidelines describe methods by which the government can assess the m- pact of a proposed transaction. Also, the guidelines offer the private sector a rational ba- sis to predict the likely reaction of the authorities to a proposed merger or acquisition, thus reducing uncertainty and unnecessary transaction costs. In close cases, the Guide- lines help to focus debate on the key factors affecting consumer welfare rather than on extraneous issues Very briefly, the Merger Guidelines require analysts to consider what products consum- ers view as alternatives for those produced by the merging parties, to define a"relevant market consisting of such products, to measure concentration among sellers in that mar- ket, and to consider the ease with which other sellers could enter. The aim of the analysis is to assess the risk that consumers will be faced with price increases(or quality deterio- ration )as a result of the proposed transaction. In addition to an analytical framework, the Guidelines establish non-binding administrative standards(in terms of permitted levels of concentration, for example) for the exercise of prosecutorial discretion. In an antitrust context the purpose of the guidelines is to provide the public with tools to predict the au thorities'decision whether or not to bring a law enforcement action to stop any given transaction. As spillover effects, the Guidelines informally restrict the discretion of prosecutors and provide authoritative analytical guidance to courts both in deciding merger cases and in other areas of antitrust law, especially those where market definition is a significant issue Mass media compete in many different product and geographic markets. Some of these markets are ordinary commercial markets for the sale of advertising, the purchase of pro- gramming, and(in the cases of multichannel video program distributors, certain internet service providers, and print media)the compilation of content packages and the provision 66 ownership concentration poses harm to competition or to consumers is precisely the ques￾tion upon which the antitrust laws and their enforcers focus. The modern approach to analysis of ownership concentration is illustrated by the frame￾work set out in the DOJ/FTC Merger Guidelines (Merger Guidelines or Guidelines). The Guidelines, while certainly not infallible, are widely respected by courts and commenta￾tors alike. The Guidelines describe methods by which the government can assess the im￾pact of a proposed transaction. Also, the Guidelines offer the private sector a rational ba￾sis to predict the likely reaction of the authorities to a proposed merger or acquisition, thus reducing uncertainty and unnecessary transaction costs. In close cases, the Guide￾lines help to focus debate on the key factors affecting consumer welfare rather than on extraneous issues. Very briefly, the Merger Guidelines require analysts to consider what products consum￾ers view as alternatives for those produced by the merging parties, to define a “relevant market” consisting of such products, to measure concentration among sellers in that mar￾ket, and to consider the ease with which other sellers could enter. The aim of the analysis is to assess the risk that consumers will be faced with price increases (or quality deterio￾ration) as a result of the proposed transaction. In addition to an analytical framework, the Guidelines establish non-binding administrative standards (in terms of permitted levels of concentration, for example) for the exercise of prosecutorial discretion. In an antitrust context the purpose of the Guidelines is to provide the public with tools to predict the au￾thorities’ decision whether or not to bring a law enforcement action to stop any given transaction. As spillover effects, the Guidelines informally restrict the discretion of prosecutors and provide authoritative analytical guidance to courts both in deciding merger cases and in other areas of antitrust law, especially those where market definition is a significant issue. Mass media compete in many different product and geographic markets. Some of these markets are ordinary commercial markets for the sale of advertising, the purchase of pro￾gramming, and (in the cases of multichannel video program distributors, certain internet service providers, and print media) the compilation of content packages and the provision