arXiv subjects

Leo Kurata

Publications and source records attributed to Leo Kurata.

4 recordsLinked to original sources

arXiv2026

Classification Aggregation with Multiple Memberships

People face the problem of classifying objects into categories while aggregating their opinions. We axiomatically study such a classification aggregation problem with multiple memberships, meaning that each individual assigns one category to every object, whereas the resulting classification may assign more than one category. Under the natural settings and axioms (i.e., Independence and Supportiveness), each of our new axioms -- Responsibility, Split Stability and Rejection Stability -- characterises what we call the junta rules. The rules assign a category to an object exactly when some member of a fixed coalition does so. The coalitions that can secure an assignment form a grill, a topological structure implied by an ultrafilter. Hence, the study parallels the literature on Arrow's theorem characterised by the decisive coalition structures. An infinite population setting is also investigated to clarify the differences among the axioms.

econ.TH↗

arXiv2026

Collective decisions under uncertainty: efficiency, ex-ante fairness, and normalization

This paper studies preference aggregation under uncertainty in the multi-profile framework and characterizes a new class of aggregation rules that can address classical concerns about Harsanyi's (1995) utilitarian rules. Our aggregation rules, which we call \textit{relative fair aggregation rules}, are grounded in three key ideas: utilitarianism, egalitarianism, and the 0--1 normalization of individual utilities. These rules are parameterized by a set of weight vectors over individuals and evaluate each ambiguous alternative by taking the minimum weighted sum of 0--1 normalized utility levels over the weight set. For the characterization, we propose two novel axioms, \textit{weak preference for mixing} and \textit{restricted certainty independence}, with normative justifications. Additional results clarify how these axioms capture the utilitarian and egalitarian attitudes of the rules.

econ.TH↗

arXiv2026

Agreement with reservation of judgment under risk

This paper studies preference aggregation under risk. In our model, each agent has an incomplete preference relation represented by a set of expected utility functions. The classical Pareto principle is silent on agreement involving indecisiveness. To examine the implications of respecting such agreement, we introduce the Paretian principle that can be applied when some individuals reserve their judgment. Our main result shows that, under this principle, for each combination of individuals' utility functions, there exists a corresponding social utility function constructed as a weighted sum of the individual ones. These aggregation rules guarantee natural properties that the standard Pareto principle fails to ensure.

econ.TH↗

arXiv2025

Reservation of Judgment and Robust Collective Decisions

This paper studies preference aggregation under ambiguity when agents have incomplete preference relations due to imprecise beliefs. We introduce the "dual" of the Pareto principle, which respects unanimity among individuals, including those with unexpressed opinions. Our first theorem shows that, in most cases, this principle leads to a dictatorial rule in taste aggregation. We argue that this stems from the problem of spurious unanimity, even when the individuals have the same prior set. By weakening the above principle to avoid respecting spurious unanimity, the second theorem characterizes novel belief-aggregation rules, under which society does not discard any combination of plausible priors.

econ.TH↗