Optimal stopping in a two-sided secretary problem

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In the "secretary problem", well-known in the theory of optimal stopping, an employer is about to interview a maximum of N secretaries about which she has no prior information. Chow et al. proved that with an optimal strategy the expected rank of the chosen secretary tends to approximately 3.87. We study a two-sided game-theoretic version of this optimal stopping problem, where men search for a woman to marry at the same time as women search for a man to marry. We find that in the unique subgame perfect equilibrium, the expected rank grows as the square root of N and that, surprisingly, the leading coefficient is exactly 1. We also discuss some possible variations.