15e Salon de Paris Club Lecture by Yukio KORIYAMA, Professor, Ecole Polytechnique “Does majority rule bring happiness to the society? – An overview of the theory of collective decision-making that prevents the tyranny of the majority”」

How should democratic decisions be made in the society? The answer to this question is not obvious, despite the discussions provided by the great philosophers of human history. While many people mistakenly recognize majority rule as a constitutive element of democracy, great thinkers such as Rousseau, Condorcet, the founding Fathers of the United States, Tocqueville and Rawls have developed arguments concerning democratic decision-making and institutional design, in which majority rule is not a necessary condition for democracy.

In this talk, we discuss the scientific methods used in collective decision-making theory. Various ideas have been developed through theoretical and empirical analysis, supported by recent advances in game theory, social choice theory, behavioral economics, experimental economics and institutional design theory. EBPM (Evidence-Based Policy Making) is a method developed in this context and known to have desirable properties in scientific decision-making, providing insights into a wide range of collective decisions, from small-scale everyday decisions to large-scale societal decisions, such as elections.

At the same time, we know from our practical experiences that there are plenty of situations in which it is impossible to make sensible decisions based solely on theories and numbers. Until recently, scientific analysis has struggled to take into account the human aspects of decision-making, such as psychological biases, fairness considerations and feelings of persuasion. We discuss desirable properties of collective decision-making that capture the human aspects of individual behavior, using the latest findings from scientific research.

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