Strategic tanking can improve matches without misreporting preferences
Strategic Tanking in Stable Matching Markets
Computer Science and Game TheoryMultiagent Systems
Summary
Sometimes in matching systems like college admissions or job placements, a person can do better by making themselves seem less attractive to some potential partners. This is different from lying about what they want—here, they just influence how others rank them. The authors show that doing this in certain ways mimics another known tactic where people shorten their own preference lists, but without changing their true preferences. More complex ways of tanking can lead to results outside the usual stable options, meaning there are more ways to improve outcomes even if others are honest.
What this means in practice
- •For market designers: Design matching platforms that anticipate and address strategic tanking tactics to ensure fairer outcomes.
- •For online dating services: Develop features that detect or mitigate strategic tanking where users influence others’ preferences indirectly.
A theory result. No direct application yet.
Authors
James P. Bailey
Abstract
Motivated by a broad literature in psychology, organizational behavior, and matching markets, we introduce strategic tanking: an agent deliberately makes themselves less attractive to selected potential partners in order to improve their eventual assignment. Unlike traditional manipulation in stable matching, a tanker does not misreport whom they prefer; instead, they influence how others rank them. We show that tanking has a striking connection to classical preference manipulation. Cutoff tanking, in which an agent tanks with every potential partner below a chosen threshold, has exactly the same effect on the stable set as truncating one's own preference list at that threshold. Thus an agent can reproduce the power of a classical truncation while leaving their own preferences unchanged and every match acceptable. Arbitrary tanking, however, can go substantially further: under proposer-deferred acceptance, tanking equilibria can lie outside the sincere stable set. More broadly, whenever the sincere stable set contains multiple matchings, profitable strategic behavior remains available through either traditional preference manipulation or tanking, even when one side is restricted to honestly reporting their own preferences.