Pairwise Justifiable Changes in Collective Choices

51 Pages Posted: 23 May 2021 Last revised: 24 Mar 2022

See all articles by Salvador Barberà

Salvador Barberà

Universitat Autònoma de Barcelona; MOVE; Barcelona School of Economics

Dolors Berga

University of Girona - Department of Economics

Bernardo Moreno

University of Malaga

Antonio Nicolò

University of Padua - Department of Economics; University of Manchester

Date Written: March 13, 2022

Abstract


Consider the following principle regarding the performance of collective choice rules. "If a rule selects alternative x in situation 1, and alternative y in situation 2, there must be an alternative z, and some member of society whose appreciation of z relative to x has increased when going from situation 1 to situation 2." This principle requires a minimal justification for the fall of x in the consideration of society: someone must have decreased its appreciation relative to some other possible alternative. On appropriately restricted domains, pairwise justifiability, along with anonymity and neutrality, characterizes Condorcet consistent rules, thus providing a foundation for the choice of the alternatives that win by majority over all others in pairwise comparisons, when they exist.

We study the consequences of imposing this requirement of pairwise justifiability on a large class of collective choice rules that includes social choice and social welfare functions as particular cases.

When preference profiles are unrestricted, it implies dictatorship, and both Arrow's and the Gibbard-Satterthwaite's theorems become corollaries of our general result.

Keywords: Pairwise justifiability, social choice functions, social welfare functions, Condorcet consistency, Arrow's theorem, Gibbard-Satterthwaite's theorem

JEL Classification: D70, D71, D78

Suggested Citation

Barberà, Salvador and Berga, Dolors and Moreno, Bernardo and Nicolò, Antonio, Pairwise Justifiable Changes in Collective Choices (March 13, 2022). Available at SSRN: https://ssrn.com/abstract=3848685 or http://dx.doi.org/10.2139/ssrn.3848685

Salvador Barberà (Contact Author)

Universitat Autònoma de Barcelona ( email )

Edifici B - Campus Bellaterra
Cerdanyola del Vallès, Barcelolna 08193
Spain
34935811814 (Phone)
34935812012 (Fax)

HOME PAGE: http://pareto.uab.es/sbarbera/

MOVE ( email )

Campus de Bellaterra-UAB Edifici B (s/n)
EDIFICI B
Cerdanyola del Vallès
, Barcelona 08193
Spain
34935812188 (Phone)
34935812012 (Fax)

HOME PAGE: http://www.movebarcelona.eu/

Barcelona School of Economics ( email )

Carrer de Ramon Trias Fargas, 25-27
Barcelona, 08005
Spain

HOME PAGE: http://bse.eu/

Dolors Berga

University of Girona - Department of Economics ( email )

Campus de Montilivi
Girona, Girona 17071
Spain

Bernardo Moreno

University of Malaga ( email )

Malaga, Málaga 29004
Spain

Antonio Nicolò

University of Padua - Department of Economics ( email )

via Del Santo 33
Padova, 35123
Italy

University of Manchester ( email )

Arthur Lewis Building
Oxford Road
Manchester, M13 9PL
United Kingdom

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