Intuitive Preference Aggregation: Tests of Independence and Consistency

Abstract

Stanford students were shown hypothetical preference profiles involving 3 to 5 voters and 2 to 6 alternatives. Profiles were constructed to test subjects' adherence to two related social choice criteria implicated in Arrow's impossibility theorem: inter-menu consistency (IMC) – which is a consequence of the collective rationality assumption – and independence of irrelevant alternatives (IIA). Subjects violated both IMC and IIA in strong numbers, and robustly across presentation methods. The results suggest that IMC and IIA are not intuitively fair principles according to these subjects. A weaker principle which is consistent with many of Arrow's philosophical justifications for IIA and IMC is defined as 'independence of unavailable alternatives' (IUA). A majority of subjects adhere to IUA in evaluating an example that yields strong violations of both IMC and IIA, but the effect is sensitive to presentation. Other principles characterizing subjects' revealed social preferences are described.