This experiment investigates contests between groups. Each group has one strong player,
with a higher valuation for the prize, and two weak players, with lower valuations. In
contests where individual efforts are perfect substitutes, all players expend significantly
higher efforts than predicted by theory. In best-shot contests, where group performance
depends on the best performer, most of the effort is expended by strong players while weak
players free-ride. In weakest-link contests, where group performance depends on the worst
performer, there is almost no free-riding and all players expend similar positive efforts
conforming to the group Pareto dominant equilibrium.