Essays on hyper-preferences, polarization and information aggregation

Abstract : In this thesis, some important problems and properties of collective decision-making are studied. In particular, first, a stability property of preference aggregation rules is introduced and some well-known classes of rules are tested in this regard. Second, measuring preferential polarization is studied, both theoretically and empirically. Finally, strategic behavior in information aggregation situations is investigated in light of a sort of bounded rationality model, both theoretically and experimentally. The stability notion studied in the first part of the thesis is imposed particularly on social welfare functions and requires that the outcome of these functions should be robust to reduction in preference submission that are argued to take place when individuals submit a ranking of alternatives when the outcomes are also restricted to be rankings. Given the preference profile of a society, that is a collection of rankings of alternatives, a compatible collection of rankings of rankings are extracted and the outcome of social welfare functions in these two levels are compared. It turns out that no scoring rule gives consistent results, although there might exist Condorcet-type rules. Polarization measures studied in second part are in form of aggregation of pairwise antagonisms in a society. The public opinion polarization in the United States for the last three decades is analyzed in light of this view, by using a well-acclaimed measure of polarization introduced in the literature of income inequality. The conclusion is that no significant trend in public opinion polarization can be claimed to exist over the last several decades. Also, an adaptation of the same measure is shown to satisfy desirable properties in lieu of ordinal preference profiles when three alternatives are considered. Furthermore, a measure that is the aggregation of pairwise differences among individuals' preferences is characterized by a set of axioms. In the final part of the thesis, information aggregation situations described as in Condorcet jury model is studied in light of cognitive hierarchy approach to bounded rationality. Specifically, a laboratory experiment is run to test the theoretical predictions of the symmetric Bayesian Nash equilibrium concept. It is observed that behavior in lab is not correctly captured by this concept that assumes a strong notion of rationality and homogeneity among individuals' behaviors. To better describe the findings in the experiment, a novel model of cognitive hierarchy is developed and shown to perform better than both strong rationality approach and previous cognitive hierarchy models. This endogenous cognitive hierarchy model is compared theoretically to previous models of cognitive hierarchy and shown to improve in certain classes of games.
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Ali Ihsan Ozkes. Essays on hyper-preferences, polarization and information aggregation. Economies and finances. Ecole Polytechnique X, 2014. English. ⟨pastel-01071827⟩

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