Solving the « selective intervention » puzzle

This paper discusses the way in which the economic literature has solved Williamson?s selective intervention puzzle: why is that vertical integration, which gives the purchasing firm more control over its trading partner, not always more profitable than vertical separation? I argue that all the models which tackle this problem share a common feature: in the contracts which describe the relations between agents, the principal still makes decisions and acts after the contract is signed. As a consequence, the greater control provided by vertical integration can affect the principal?s ex-post behavior in ways which are ex-ante point of view detrimental to its profits.