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Basic Geometry of Voting -- Copyright -- PREFACE -- CONTENTS -- CHAPTER I FROM AN ELECTION FABLE TO ELECTION PROCEDURES -- CHAPTER II GEOMETRY FOR POSITIONAL AND PAIRWISE VOTING -- CHAPTER III THE PROBLEM WITH CONDORCET -- CHAPTER IV POSITIONAL VOTING AND THE BC -- CHAPTER V OTHER VOTING ISSUES -- NOTES -- REFERENCES -- INDEX.

Over two centuries of theory and practical experience have taught us that election and decision procedures do not behave as expected. Instead, we now know that when different tallying methods are applied to the same ballots, radically different outcomes can emerge, that most procedures can select the candidate, the voters view as being inferior, and that some commonly used methods have the disturbing anomaly that a winning candidate can lose after receiving added support. A geometric theory is developed to remove much of the mystery of three-candidate voting procedures. In this manner, the spectrum of election outcomes from all positional methods can be compared, new flaws with widely accepted concepts (such as the "Condorcet winner") are identified, and extensions to standard results (e.g. Black's single-peakedness) are obtained. Many of these results are based on the "profile coordinates" introduced here, which makes it possible to "see" the set of all possible voters' preferences leading to specified election outcomes. Thus, it now is possible to visually compare the likelihood of various conclusions. Also, geometry is applied to apportionment methods to uncover new explanations why such methods can create troubling problems

AbstractFeatures of graphs that hinder finding closed paths with particular properties, as represented by the Traveling Salesperson Problem—TSP, are identified for three classes of graphs. Removing these terms leads to a companion graph with identical closed path properties that is easier to analyze. A surprise is that these troubling graph factors are precisely what is needed to analyze certain voting methods, while the companion graph's terms are what cause voting theory complexities as manifested by Arrow's Theorem. This means that the seemingly separate goals of analyzing closed paths in graphs and analyzing voting methods are complementary: components of data terms that assist in one of these areas are the source of troubles in the other. Consequences for standard decision methods are in Sects. 2.5, 3.7 and the companion paper (Saari in Theory Decis 91(3):377–402, 2021). The emphasis here is on paths in graphs; incomplete graphs are similarly handled.

Arrow's Impossibility Theorem and Sen's Minimal Liberalism example impose 'impossibility' roadblocks on progress. A reinterpretation explained in this article exposes what causes these negative conclusions, which permits the development of positive resolutions that retain the spirit of Arrow's and Sen's assumptions. What precipitates difficulties is surprisingly common, and it affects most disciplines. This insight identifies how to analyze other puzzles such as conflicting laws or controversies over voting rules. An unexpected bonus is that this social science issue defines a research agenda to address the 'dark matter' mystery confronting astronomers.

We develop a geometric approach to identify all possible profiles that support specified votes for separate initiatives or for a bundled bill. This disaggregation allows us to compute the likelihood of different scenarios describing how voters split over the alternatives and to offer new interpretations for pairwise voting. The source of the problems—an unanticipated loss of available information—also explains a variety of other phenomena, such as Simpson's paradox (a statistical paradox in which the behavior of the "parts" disagrees with that of the "whole") and Arrow's theorem from social choice.