We investigate Cournot and Stackelberg mixed duopoly models where a stateowned public firm maximizing domestic social surplus, and a foreign firm searching to maximize its own profit, compete. First, we establish the existence and uniqueness results for the Cournot scheme, and propose the agents' classification as strong or weak according to the agent's optimal reaction function properties at the Cournot equilibrium. Then we examine a desirable role (either leader or follower) of both firms in the Stackelberg schemes and compare the profits and domestic social surplus and the production volumes at each type of Stackelberg equilibrium.

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In this paper, we develop a bi-level human migration model using the concept of conjectural variations equilibrium (CVE). In contrast to previous works, here we construct a bi-level programming model. The upper level agents are municipalities of competing locations, whose strategies are investments into infrastructures of the locations (cities, towns, etc.). These investments aim at making the locations more attractive for both the residents and potential migrants from other locations. At the lower level of the model, the present residents (grouped into professional communities) are also considered as potential migrants to other locations. They make their decision where to migrate (if at all) comparing the expected values of the utility functions of the destinations and original locations, which are estimated by taking into account their group's conjectures concerning equilibrium migration flows between the involved locations. Applying a special technique to verify the consistency of the conjectures (influence coefficients), the existence and uniqueness results for the consistent conjectural variations equilibrium (CCVE) are established.

Structural changes in the European natural gas market such as liberalization, increasing domestic demand, and increasing import dependency have triggered new attempts to model these markets accurately. In this paper, we propose an exhaustive model of the European natural gas supply including the possibility of strategic behaviour of the agents along the value-added chain. We structure it as a two-stage-game with natural gas exports to Europe (first stage) and wholesale trade within Europe (second stage). The case of non-cooperative Cournot competition at both stages proves to be the most realistic scenario. The results of the perfect competition and cartel scenario are also presented. Our results suggest that the main suppliers of natural gas to Europe (Russia, Algeria, the Netherlands, Norway) remain dominant, but that they are complemented by overseas supplies of liquefied natural gas (LNG). The model also enables us to identify transport infrastructure bottlenecks where transport capacity constraints are binding.

The study examines the period of the Great Depression and analyzes several measures taken by the US President Roosevelt’s government that allowed the country to get out of the crisis. An analysis and proof of the correctness of the measures chosen to exit from the crisis was conducted using econometric models and the use of statistics. Techniques for overcoming crises are relevant for all countries. This study adapts an innovative perspective in that it used the sequence of the Cobb–Douglas type function including different types of factors, and applied fuzzy regression methods.