Variable Competence and Collective Performance: Unanimity Versus Simple Majority Rule

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Under the unanimity rule, a single voter may alter a decision that is unanimously accepted by all other voters. Under the simple majority rule, the impact of such a voter diminishes. This paper examines the marginal effect of competence on the collective performance—the likelihood of reaching a correct decision. It is shown that adding an incompetent voter to the group is inferior (superior) to giving up an existing competent voter, when the decision mechanism is the unanimity (simple majority) rule. The negative impact of an incompetent voter cannot (can) always be balanced by adding a competent one under the unanimity (simple majority) rule. Moreover, improving a single voter’s competence may have a greater effect on the collective performance under the simple majority rule relative to the unanimity rule.

Original languageEnglish
Pages (from-to)157-167
Number of pages11
JournalGroup Decision and Negotiation
Issue number1
Early online date5 Nov 2019
StatePublished - 1 Feb 2020


  • Collective performance
  • Simple majority rule
  • Unanimity rule
  • Voters’ competence

All Science Journal Classification (ASJC) codes

  • General Decision Sciences
  • Arts and Humanities (miscellaneous)
  • Management of Technology and Innovation
  • General Social Sciences
  • Strategy and Management


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