24 November 2025We study experimentally a three-person sequential and symmetric coalition formation game with empty core. The game was played repeatedly, with randomly re-matched groups. We observe that over 86% of the realized coalitions are two-person coalitions. Three players coalitions are often observed in early periods but are frequently rejected. Equal splits are the most frequently observed divisions among coalition members, and their frequency increases sharply over time. We propose a modification of von Neumann and Morgenstern (1944)’s notion of the vNM stable set to account for our results by introducing a bargaining cost.