2 heoretical considerations The literature on the interrelationship of markets is strongly connected with media markets of several kinds. Most theoretical and empirical studies deal with the newspaper sector and focus on United States, Great Britain, and Australia While some others concern media like television or radio, but only few of them investigate the interdependency of the markets. For this reason most of the literature surveyed in this paper is related to newspaper advertising and reader markets Theoretical considerations of interrelated markets are rare. Only few studies deal with the interdependency of reader and advertising markets or the influence of different cost structures. Moreover, none of these articles analyse features like quality provision or habit effectss. Only few analyse separate(for example oligopolistic) market structures on advertising and reader markets. Actually, most studies consider monopolistic media firms, which is surely an appropriate and realistic assumption for most reader markets but(also due to the possibility of inter media competition) not necessarily for advertising market As stated above, studies on(inter)related markets are mostly concerned with traditional media like newspapers or magazines. Correspondingly, the first arti cle of this kind by Corden(1952) dealing with demand dependency, analyses the relationship between newspapers'advertising and reader markets. Corden con- siders the optimisation problem of a newspaper firm using geometric techniques within a static framework. However. Corden does not consider interrelated. but only related markets. On the one hand, he asserts that circulation is an impor tant variable for both markets, but on the other hand he neglects to consider the influence of advertising on the demand for copies, even though he is aware of this2 Theoretical considerations The literature on the interrelationship of markets is strongly connected with media markets of several kinds. Most theoretical and empirical studies deal with the newspaper sector and focus on United States, Great Britain, and Australia. While some others concern media like television or radio, but only few of them investigate the interdependency of the markets. For this reason most of the literature surveyed in this paper is related to newspaper advertising and reader markets. Theoretical considerations of interrelated markets are rare. Only few studies deal with the interdependency of reader and advertising markets or the influence of different cost structures. Moreover, none of these articles analyse features like quality provision or habit effectss. Only few analyse separate (for example oligopolistic) market structures on advertising and reader markets. Actually, most studies consider monopolistic media firms, which is surely an appropriate and realistic assumption for most reader markets but (also due to the possibility of inter media competition) not necessarily for advertising markets. As stated above, studies on (inter)related markets are mostly concerned with traditional media like newspapers or magazines. Correspondingly, the first arti￾cle of this kind by Corden (1952) dealing with demand dependency, analyses the relationship between newspapers’ advertising and reader markets. Corden con￾siders the optimisation problem of a newspaper firm using geometric techniques within a static framework. However, Corden does not consider interrelated, but only related markets.3 On the one hand, he asserts that circulation is an impor￾tant variable for both markets, but on the other hand he neglects to consider the influence of advertising on the demand for copies, even though he is aware of this 6