Contests between groups are plagued by intra-group externalities (freeriding). Yet, costless incentive schemes that entirely avoid free-riding within a group might not be desirable, neither individually nor socially. In contests among two groups, a relatively weak (i.e., small or unproductive)...

Lecture on the first SFB/TR 15 meeting, Gummersbach, July, 18 - 20, 2004: This paper models the trade-off between production and appropriation in the presence of simultaneous inter- and intra-group conflicts. The model exhibits a ' group cohesion effect ': if the contest between the groups...