  This paper studies strategic decentralization in binary choice composite
network congestion games. A player decentralizes if she lets some autonomous
agents to decide respectively how to send different parts of her stock from the
origin to the destination. This paper shows that, with convex, strictly
increasing and differentiable arc cost functions, an atomic splittable player
always has an optimal unilateral decentralization strategy. Besides, unilateral
decentralization gives her the same advantage as being the leader in a
Stackelberg congestion game. Finally, unilateral decentralization of an atomic
player has a negative impact on the social cost and on the costs of the other
players at the equilibrium of the congestion game.
