Equal Split in an Almost Ultimatum Game: Field Evidence from the Informal Market for Group Train Travel

In this paper we make use of a unique dataset collected in the train station of Kiel, Germany. A group ticket is used by individual proposers who search to take co-travelers for a fixed price shortly before the train departure. The behavior resembles an ultimatum bargaining game to the extent that proposers offer a specific price and travelers usually accept or reject. We observe that the average price is an equal split of the ticket price by the most frequently observed number of co-travelers. This finding support the conjuncture that the equal split is a focal point even in situations with clear asymmetry between the parties. Moreover, using computer simulations we are able to identify some sufficient conditions for the observed distribution of prices. Finally, we observed that the probability to accept an offer is decreasing with the price and increasing when the offer is made right before the train departure time.