In competitive economies  in which information is asymmetric (because e.g., of moral hazard or adverse selection) contracts are traded in markets. Economies in which exclusive contractual relationships  can be implemented  have  fundamentally different properties from those of economies in which contracts are non-exclusive. Non-exclusive contracts do not require the observability of all of the agents’ trades. 

The following papers study existence and efficiency for economies in which contractual relationships are non-exclusive, in Walrasian as well as strategic economic environments. The last paper addresses the issue of the convergence of strategic equilibria to Walrasian equilibria under replication.  

Efficient Competitive Equilibria with Adverse Selection (with P. Gottardi, 2000, forthcoming, Journal of Political Economy

    General Competitive Analysis with Asymmetric Information, (with P. Gottardi), Journal of Economic Theory, 87(1), 1-48, 1999.

Competitive Equilibria with Asymmetric Information: Existence with Entry Fee (with P. Gottardi)   Review of Economics Dynamics, 6, 313-38, 2003. 

Markets as Contracts (with J. Geanakoplos, P. Gottardi,  E. Minelli, H. Polemarchakis), forthcoming in Journal of Mathematical  Economics.

Moral Hazard and Non-exclusive Contracts (with D. Guaitoli);   Rand Journal of Economics, 35(2), 306-28, 2004

             Computational Appendix     There is an  error in the paper;  see the note by Attar-Chassagnon forthcoming on the Journal of Mathematical Economics.

A Note on Convergence to Competitive Equilibria in Economies with Moral Hazard (with P. Gottardi and D. Guaitoli), in "The Theory of Markets",  in  P.J.J. Herings, G. van der Laan, and A.J.J. Talman (eds.), North Holland, Amsterdam, 1998.

The following papers study economies in which financial  markets are endogenously incomplete because of transactions costs. It is shown that some disturbing equilibrium properties of incomplete markets economies with exogenously incomplete markets (notably, the real indeterminacy of equilibria documented by Balasko-Cass and Geanakoplos-Mas Colell, and studied by Magill-Quinzii and many others)  are not robust to the introduction of optimizing intermediaries who design financial securities.

General Equilibrium with Endogenously Incomplete Financial Markets, Journal of Economic Theory, 82(1), 19-45, 1998. 

 At The Roots of Indeterminacy, in P.P. Battigalli et al., Markets and Games, Basil Blackwell, 1998.   

The following paper studies integrate issues of corporate finance (e.g., management compensation) and asset prices (e.g., the  CAPM).

Managerial Hedging, Equity Ownership, and Firm Value (with V. Acharya), forthcoming on Rand Journal of Economics, 2008.

                                                                Appendix

Optimal Financial Integration and Security Design (with V. Acharya), Journal of  Business, 78(6), 2397-433, 2005.

Exclusive Contracts and the Institution of Bankruptcy, (with A. Rampini), Economic Theory, 27(2), 277-304, 2006.

Managerial Hedging and Portfolio Monitoring (with P. Gottardi and A. Rampini), Journal of the European Economic Association, 6, 158–209, 2008

Finally, my recent work with Adriano Rampini on Public Finance/Optimal taxes:

Markets as beneficial constraints on the government (with A. Rampini), Journal of Public Economics 90, 601-629, 2006.