We analyze reciprocal market sharing agreements by which firms commit not to enter each other's territory in oligopolistic markets and procurement auctions. The set of market sharing agreements defines a collusive network. We characterize stable collusive networks when firms and markets are...

In a Cournot duopoly where firms incur a fixed cost for serving each market, collusion is easier to sustain with production quotas if the fixed cost is small enough, and with market sharing agreements if it is large enough.