Contests are situations in which a set of agents compete for a valuable object, rent or award. The present paper analyzes difference-form group contests, that is, contests fought among groups and where their probability of victory depends on the difference of their effective efforts. First, we...

I analyse a group contest in which groups decide over two dimensions of membership-exclusivity: whether a member is allowed to join the group at all, and whether this member is allowed to join another group as well. If the prize is mostly private, group leaders do not offer membership in...