The changes in demand for beer and sake - The demand growth models of competition

Two models are introduced which describe the secular changes of demand in beer and sake. These models: which are given by a set of differential equations, try to describe the demand shift from sake to beer. The competition to be studied in this paper is restricted to this demand shift, The first model is simple. It assumes that the secular trend of beer-demand is expressed by the Logistic Curve. And a certain rate of sake-demand is absorbed into the beef-demand, as the time elapses. The second model, which is rather sophisticated. is obtained by examining the first model. It assumes that the changes in disposable income are explained by the changes of two components, each of which is described by the Logistic Curve. A change of beer-demand is explained by the secular changes of these components. As each equation, which appears in these models, is determined with the given parameters, the method of curve fitting is applied to the time-series data of beer and sake demand. We are to estimate a set of parameters (empirical constants) so that the empirical formulae which explain the actual secular trend of sake and beer demands, may be determined, The results obtained by these models can explain the actual secular trend of beer and sake demand. Moreover by examining the analytical properties of the empirical formulae obtained! the actual change of demands for beer and sake can be described.