interrelated markets Especially the print media exhibits large economies of scale, as a number of empirical studies on newspapers and magazines have shown. Moreover, the ex- istence of these scale economies is frequently asserted as a main reason for the persistent concentration in media markets and, therefore, for market power. Fur thermore, intra-industry concentration and also cross-ownership of media prod- ucts is a characteristic worth mentioning. Not only in Germany, but also in Europe, the United States and Australia, there are several firms which operate in different media branches such as print media, radio broadcasting and television Some few examples of the largest worldwide acting cross-ownership firms are AOL Time Warner, Bertelsmann, Viacom, or Rupert Murdoch,s News Corporation An important requirement for analyses on interrelated demand is the defini- tion of the relevant markets. This is not always a trivial task. Even if the primary markets, as for example copy markets, are concentrated, it is not necessarily the case that the secondary markets are also highly concentrated as well. Because of possible substitutional relationships, especially to advertising space in vari- ous different media products, market delineation is not identical for primary and secondary markets. The consequence are asymmetries with respect to markets structures A further characteristic of media products is an effect that can be described in terms of habit formation or addictive behaviour. Newspaper habit and par ticularly Internet addiction(see for example Stein 1997, Griffith 1999 or Beard 2002) are phenomena subject to psychological and psychiatric research. Not only subscriptions, but also newsstand sales seem to be path depending. Moreover some mass media have public good properties because both, radio and TV broad casting are neither not rival and to some extend not excludable. Note. that thisinterrelated markets. Especially the print media exhibits large economies of scale, as a number of empirical studies on newspapers and magazines have shown. Moreover, the ex￾istence of these scale economies is frequently asserted as a main reason for the persistent concentration in media markets and, therefore, for market power. Fur￾thermore, intra-industry concentration and also cross-ownership of media prod￾ucts is a characteristic worth mentioning. Not only in Germany, but also in Europe, the United States and Australia, there are several firms which operate in different media branches such as print media, radio broadcasting and television. Some few examples of the largest worldwide acting cross-ownership firms are AOL Time Warner, Bertelsmann, Viacom, or Rupert Murdoch’s News Corporation. An important requirement for analyses on interrelated demand is the defini￾tion of the relevant markets. This is not always a trivial task. Even if the primary markets, as for example copy markets, are concentrated, it is not necessarily the case that the secondary markets are also highly concentrated as well. Because of possible substitutional relationships, especially to advertising space in vari￾ous different media products, market delineation is not identical for primary and secondary markets. The consequence are asymmetries with respect to markets structures. A further characteristic of media products is an effect that can be described in terms of habit formation or addictive behaviour. Newspaper habit and par￾ticularly Internet addiction (see for example Stein 1997, Griffith 1999 or Beard 2002) are phenomena subject to psychological and psychiatric research. Not only subscriptions, but also newsstand sales seem to be path depending. Moreover, some mass media have public good properties because both, radio and TV broad￾casting are neither not rival and to some extend not excludable. Note, that this 4