Social choice theory contains a number of deductive theorems on voting Methods' properties, in particular "non-existence" theorems, stating that there is no voting method complying particular rationality condition (as insusceptibility to strategic voting). These theorems, though theoretically important, have limited practical implications. When no voting method guarantees rational choice, the question of risk level connected with particular methods is raised. Such a question can be partly answered by means of computer simulations. Although simulations' results have no deductive quality, often they could be treated as statistical hypotheses. Even if statistical interpretation is impossible, simulations' results could be helpful in resolving practical problems.

Analysis of vulnerability of selected social choice methods to strategic voting is presented in the article. Selected methods are: plurality voting, the Borda count and approval voting. Applied procedure allowed strategic voting of unlimited number of voters. With each method voters knew the outcome of the sincere voting, consistent with their real preferences. 24 variants differed on voting parameters; for each variant 1000 random profiles of preferences have been analyzed. Results are different from expected.

The article presents an analysis of the effects of the list apparentment institution introduced in the electoral rule for the sejmik of voivodship (regional council) and of some other changes which also had significant consequences. The effect analysis of these institutional solutions required primarily a comparison of specific political parties’ election results with the results these parties would have got under the „old” electoral rule, assuming no change in voters’ preferences resulting from the change in law. The electoral rule amendment had a significant impact on the results of specific parties, as measured by the number of mandates gained. Then, the authors investigated a number of alternative coalition strategies available to political parties, elaborating on the issue of effectiveness in actions undertaken by collective actors such as political parties. The authors proved that the results of the elections concerned depended on coalition strategies, rather than on election rules. Some players in the electoral game failed to achieve effectiveness in the attainment of the ultimate objective, i.e. to maximise the number of mandates gained, but the assessment of effectiveness provides different results if we assume that an important objective (though not equally important) was to maximise the results of the relevant bloc formed by apparentment. A matter of concern in the new electoral rule is the violation in 26% of constituencies of the monotonny criterion in the distribution of mandates resulting from the distribution of votes. In their concluding remarks, the authors put forward a proposal for a change in the electoral rule that better reflects the profiles of individual preferences in the social choice, while maintaining the apparentment institution.

Auction theory belongs to one of the most important applications of game theory in economics. The possibility of presenting an auction as a game facilitates its strategic analysis and the comparison of different auction rules in relation to the player`s expected payoffs. The aim of this paper is to review basic knowledge concerning symmetric auctions for which we assume that all bidders possess the same amount of information concerning sold objects and all bidders` valuations are independent as well as identically distributed random variables. The first part of this paper is devoted to unit object auctions. We will present strategic analysis of the family of such auctions within the model proposed by Riley and Samuelson (1981). The second part of the thesis will be devoted to the description of different types of multiple object auctions: the simultaneous ascending auction and the Anglo-Dutch auction which have been created to sell telecommunication licenses, the combinatorial auction, during which buyers receive the possibility to place their offers on sets of items, and finally the double auction in which many buyers and sellers participate.