Efficient Collective Decision-Making, Marginal Cost Pricing, and Quadratic Voting Nicolaus Tideman* Department of Economics, Virginia Polytechnic Institute and State University Blacksburg, VA 24061
[email protected] Phone: 540-231-7592; Fax: 540-231-9288 Florenz Plassmann Department of Economics, State University of New York at Binghamton Binghamton, NY 13902-6000
[email protected] Phone: 607-777-4934; Fax: 607-777-2681 This version: February 22, 2016 Abstract We trace the developments that led to quadratic voting, from Vickrey’s counterspeculation mechanism and his second-price auction through the family of Groves mechanisms, the Clarke mechanism, the expected externality mechanism, and the Hylland-Zeckhauser mechanism. We show that these mechanisms are all applications of the fundamental insight that for a process to be efficient, all parties involved must bear the marginal costs of their actions. JEL classifications: D72, D82 Keywords: Quadratic Voting, Expected externality mechanism, Vickrey-Clarke-Groves mechanism, Hylland-Zeckhauser mechanism. * Corresponding author. We thank Glen Weyl for helpful comments. 1. Introduction Quadratic voting is such a simple and powerful idea that it is remarkable that it took economists so long to understand it. At one level, its discovery was a flash of insight. At another level, the discovery is the latest step in a series of incremental understandings over more than half a century. Our account of the history of insights that led up to quadratic voting begins with a detour. In his 1954 paper The pure theory of public expenditures, Paul Samuelson set out the conditions for efficient provision of public goods and told us that we should not expect to ever achieve those conditions.