The El Farol bar model, proposed to study the dynamics of competition of ag
ents in a variety of contexts (W.B. Arthur, Amer. Econ. Assoc. Fap. Proc. 8
4, 408 (1994)) is studied. We characterize in detail the three regions of t
he phase diagram (efficient, better than random and inefficient) of the sim
plest version of the model (D. Challet! Y.-C. Zhang, Physica A 246, 407 (19
97)). The efficient region is shown to have a rich structure, which is inve
stigated in some detail. Changes in the payoff function enhance further the
tendency of the model towards a wasteful distribution of resources.