著者

富山 慶典

出版者

群馬大学社会情報学部

雑誌

群馬大学社会情報学部研究論集 (ISSN:13468812)

巻号頁・発行日

no.4, pp.55-67, 1997-07-28

---

Some relationship among the individual choice competence, the number of individuals in the group, its decision rule and the collective choice competence was initially investigated in Condorcet's Jury Theorem. Although several researchers have devloped the theorem in different directions, they in common assume implicitly one collective choice area and introduce only the individual choice competence for the area. In reality, however, there may exist multiple collective choice areas such as 'management strategy and personnel changes planning' and the individual choice competencies may be different for the corresponding area such that 'he/she is good at management strategy but not personnel changes planning'. Under the multiplicity of choice areas and the difference in competencies, how should the group assign what members in it to what collective choice area? Tomiyama (1991) extends the basic model under Jury Theorem to the model of two collective choice areas and formulates in general the group two-decomposition problem. It also gives a solution to this problem under the complete homogeneity assumption that all of the members in the group have the same competence of individual choice for all of the collective choice areas. This paper analyses the problem under the heterogeneity assumption. It is proved that individual rationality and social rationallty may not be compatible. The high-competence decomposition is used to represent individual rationality, and the maximum-sum decomposition and the minimum-difference decomposition are used to represent social rationality. Finally, some unsolved problems are showed.