Kotowski, Maciej. "A Perfectly Robust Approach to Multiperiod Matching Problems." HKS Faculty Research Working Paper Series RWP19-016, May 2019 (Updated August 2019).


Many two-sided matching situations involve multi-period interaction. Traditional co-operative solutions, such as pairwise stability or the core, often identify unintuitive out-comes (or are empty) when applied to such markets. As an alternative, this study proposes the criterion of perfect a-stability. An outcome is perfect a-stable if no coalition prefers an alternative assignment in any period that is superior for all plausible market continuations. The solution posits that agents have foresight about the future, but cautiously evaluate possible outcomes. A perfect a-stable matching exists, even when assignments are inter-temporal complements. The perfect a-core, a stronger solution, is nonempty under standard regularity conditions, such as history-independence. Our analysis extends to markets with arrivals and departures, transfers, and many-to-one assignments.