EN
This paper includes a model of price movements (market values) based on the general premise that price is equivalent to market value, as well as other premises. A concrete case involving the application of the dynamic theory of models to a description of the behaviour of price and use in a perfect competitive market is analyzed. The model is constructed from a first-order linear ordinary differential equation and shows, given the market assumptions referred to above for certain types of commodity (such as furs or textiles), that the theory conforms closely to practice, which can be used to construct an estimation theory (for details see Drozen, 2003).