The question of the sales performance achieved through radio campaigns - not so much in tactical as in strategic terms - was foremost in the authors mind in developing an econometric model of turnover activities. The model developed was designed not only to take into account media expenditure but also to include other important parameters relevant to turnover such as pricing and distribution. Data concerning specific brands of yoghurt are used as an example to test this model and its data is studied in detail.
Since January 1 st 1985 GfK TV Research has been carrying out continuous TV audience research in the Federal German Republic and (West) Berlib, at first on behalf of the public-service TV stations, ARD/ARW and ZDF, and meanwhile also for the two major private broadcasters, RTL plus und SAT.l. With our daily recording of TV audience behaviour now in its 6th year, the question of reliability and validity of our results with regard to the changing of panel households is becoming the focus of attention in our control procedures. Particularly in view of the relatively costly requirements in terms of measuring techniques which are needed to establish continuous TV audience behaviour, it is inevitable that the question of stability or variability in the original sample survey is asked. concrete terms, we are considering the problem of whether the question of the way of changing panel members - fluctuation or rotation - is relevant for the quality of the TV panel. By fluctuation we understand the replacement of panel households who le ave with new panel households who improve the structure (of the Panel). By rotation, over and above that, we understand the replacement of a Previously fixed number of panel households' membership of the panel is also limited. In order to discuss the problem of panel mortality or focussed station within the context of TV audience research at as many levels as possible, we will deal in the following section with: 1. the theoretical treatises on the subject of panel fluctuation and panel rotation. 2. the various applications within the framework of European TV audience research. 3. experiences in TV audience research in the Federal German Republic. 4. Finally we want to draw a conclusion on the basis of the first three sections: fluctuation or rotation.