Gale–Shapley algorithm: Difference between revisions

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The Gale–Shapley algorithm is a [[truthful mechanism]] from the point of view of the proposing side. This means that no proposer can get a better matching by misrepresenting their preferences. Moreover, the Gale–Shapley algorithm is even ''group-strategy proof'' for proposers, i.e., no coalition of proposers can coordinate a misrepresentation of their preferences such that all proposers in the coalition are strictly better-off.{{r|dubins-freedman}} However, it is possible for some coalition to misrepresent their preferences such that some proposers are better-off, and the others retain the same partner.{{r|huang}}
 
The Gale–Shapley algorithm is non-truthful for the non-proposing participants. Each may be able to misrepresent their preferences and get a better match.{{r|sisterhood}} However, successful misrepresentation requires knowledge of the other agents' preferences; without such knowledge, misrepresentation can make the agent worse-off. Moreover, even after the agent sees the final matching, he/she cannot deduce a strategy that would guarantee him/her a better outcome in hindsight. This makes GSthe Gale–Shapley algorithm a [[Regret-free mechanism|''regret-free truth-telling mechanism'']]. Moreover, in GSthe Gale–Shapley algorithm, truth-telling is the only strategy that guarantees no regret;. The andGale–Shapley GSalgorithm is the only regret-free mechanism in the class of quantile-stable matching mechanisms.<ref>{{Cite journal |last=Fernandez |first=Marcelo Ariel |date=2020-07-31 |title=Deferred acceptance and regret-free truth-telling |url=https://ideas.repec.org//p/jhu/papers/65832.html |journal=Economics Working Paper Archive |language=en}}</ref>
 
==Generalizations==