December 19, 1999 (Revised) <p> At least three different "envelope theorems" have proved useful for economic analysis. One applies to unconstrained optimization problems with parameterized objectives and unique solutions, a second to constrained, smooth concave maximization problems in which both...</p>

December 8, 1997 (Revised April 21, 1999) <p> We review the uses of economic theory in the initial design and later improvement of the "simultaneous ascending auction," which was developed initially for the sale of radio spectrum licenses in the US, with efficiency of the final allocation as the...</p>

Forthcoming in the American Economic Review <p>The LeChatelier principle, in the form introduced into economics by Samuelson, asserts that at a point of long-run equilibrium, the derivative of long-run compensated demand with respect to own price is larger in magnitude than the derivative of...</p>

We identify two sufficient conditions for games with strategic complementarities to have a unique equilibrium that is "strongly coalition-proof," that is, immune to incentive-compatible deviations by coalitions. If a Nash equilibrium is unique, then it is strongly coalition-proof. Also, if each...

March 2003 <p> We introduce a two-sided matching model with contracts that subsumes and extends the Gale-Shapley matching model, the Kelso-Crawford labor market model and the Ausubel-Milgrom package auction model. We identify the maximal set of preferences over contracts for which a stable match...</p>

March 2002 <p> A family of ascending package auction models is introduced in which bidders may determine their own packages on which to bid. In the proxy auction (revelation game) versions, the outcome is a point in the core of the exchange economy for the reported preferences. When payoffs are...</p>