Quadratic voting and the public good: introduction

This introduction to the Public Choice special issue on "quadratic voting (QV) and the public good" provides an opinionated narrative summary of the contents and surveys the broader literature related to QV. QV is a voting rule, proposed by one of us Weyl (Quadratic vote buying. http://goo.gl/8YEO73, 2012), Lalley and Weyl (Quadratic voting. https://papers.ssrn.com/sol3/Papers.cfm? abstract_id=2003531, 2016) building off earlier work by Groves and Ledyard (Econometrica 45(4):783-810 1977a), Hylland and Zeckhauser (A mechanism for selecting public goods when preferences must be elicited, Kennedy School of Government Discussion Paper D, 70, 1980), where individuals buy as many votes as they wish by paying the square of the votes they buy using some currency. An appreciation of the history of research in the field suggests that QV is uniquely practically relevant compared to the other approximately Pareto-efficient mechanisms economists have proposed for collective decisions on public goods. However, it faces a number of sociological and ethical concerns regarding how a political system organized around QV would achieve the efficiency aims stated in abstract theory and whether the pure aggregate income-maximizing definition of efficiency QV optimizes in its simplest form is desirable. The papers in this volume flesh out and formalize these concerns, but also provide important responses in two ways: by suggesting domains where they are unlikely to be applicable (primarily related to survey research of various kinds) and versions of QV (using an artificial currency) that maintain many of QV's benefits while diffusing the most important critiques. Together this work suggests both a practical path for applying QV in the near-term and a series of research questions that would have to be addressed to broaden its application.