||The dissertation consists of three standalone essays on dynamic models in economics. The first essay shows that both the excess supply and the excess supply price are given by two variables: the well-known inventory gap and the price gap defined as the gap between the sales price and the sellers’ costs. Empirical relevance of this price gap is shown on the panel of EU countries. The second essay concerns to banking: It provides a model of development of the probability of default of the individual client (non-entrepreneur). The result depends on the exogenous macroeconomic variables. The third essay proposes a method, how to correct predictions of the chaotic systems, which have unpredictable dynamics in the long term.