Vertical Foreclosure in Experimental Markets

We report the results of experiments designed to test recent theories of vertical foreclosure. Consistent with the theory, vertical integration improves the upstream firm's ability to commit to restricting output to the monopoly level, as does the use of public contracts. Public contracts are not a perfect substitute for vertical integration, however: integration allows more surplus to be extracted from the unintegrated downstream firm, a bargaining effect that has been underemphasized in the recent foreclosure literature. Motivated by some observations that are difficult to reconcile with existing theory, we extend the theory to allow downstream firms to have heterogeneous (rather than purely passive or symmetric) out-of-equilibrium beliefs.