Research
Chain Stability in Trading Networks
(joint with John W. Hatfield, Scott D. Kominers, Michael Ostrovsky, and Alexander Westkamp)
Theoretical Economics, v.16(1), 2021, pp. 197-234
Extended abstract, Proceedings of the 2018 ACM Conference on Economics and Computation, (2018), pp. 617-618.
Abstract: In a general model of trading networks with bilateral contracts, we propose a suitably adapted chain stability concept that plays the same role as pairwise stability in two-sided settings. We show that chain stability is equivalent to stability if all agents’ preferences are jointly fully substitutable and satisfy the Laws of Aggregate Supply and Demand. In the special case of trading networks with transferable utility, an outcome is consistent with competitive equilibrium if and only if it is chain stable.
Serial Dictatorship Mechanisms with Reservation Prices: Heterogeneous Objects
(joint with Bettina E. Klaus)
Social Choice and Welfare, v.57(1), pp. 145-162, 2021.
Abstract: We adapt a set of mechanisms introduced by Klaus and Nichifor (2019), serial dictatorship mechanisms with (individual) reservation prices, to the allocation of heterogeneous indivisible objects, e.g., specialist clinic appointments. We show how the characterization of serial dictatorship mechanisms with reservation prices for homogeneous indivisible objects (Klaus and Nichifor, 2019, Theorem 1) can be adapted to the allocation of heterogeneous indivisible objects by adding neutrality: mechanism φ satisfies minimal tradability, individual rationality, strategy-proofness, consistency, independence of unallocated objects, neutrality, and non wasteful tie-breaking if and only if there exists a reservation price vector r and a priority ordering ≻ such that φ is a serial dictatorship mechanism with reservation prices based on r and ≻.
Serial Dictatorship Mechanisms with Reservation Prices
(joint with Bettina E. Klaus)
Economic Theory, v.70, October 2020, pp. 665-684.
Abstract: We propose a new set of mechanisms, which we call serial dictatorship mechanisms with individual reservation prices for the allocation of homogeneous indivisible objects, e.g., specialist clinic appointments. We show that a mechanism φ satisfies minimal tradability, individual rationality, strategy-proofness, consistency, independence of unallocated objects, and non wasteful tie-breaking if and only if there exists a reservation price vector r and a priority ordering ≻ such that φ is a serial dictatorship mechanism with reservation prices based on r and ≻. We obtain a second characterization by replacing individual rationality with non-imposition. In both our characterizations r, ≻, and φ are all found simultaneously and endogenously from the properties. Finally, we illustrate how our model, mechanism, and results, capture the normative requirements governing the functioning of some real life markets and the mechanisms that these markets use.
Comparative Statics for Size-Dependent Discounts in Matching Markets
(joint with David Delacrétaz and Scott D. Kominers)
Journal of Mathematical Economics, v.90, October 2020, pp. 127-131
Abstract: We prove a natural comparative static for many-to-many matching markets in which agents’ choice functions exhibit size-dependent discounts: reducing the extent to which some agent discounts additional partners leads to improved outcomes for the agents on the other side of the market, and worsened outcomes for the agents on the same side of the market. Our argument draws upon recently developed methods bringing tools from choice theory into matching.
Full Substitutability
(joint with John W. Hatfield, Scott D. Kominers, Michael Ostrovsky, and Alexander Westkamp)
Theoretical Economics, v.14(4), November 2019, pp. 1535-1590.
Extended abstract, Proceedings of the 16th ACM Conference on Economics and Computation, (2015), pp. 39-40.
Abstract: Various forms of substitutability are essential for establishing the existence of equilibria and other useful properties in diverse settings such as matching, auctions, and exchange economies with indivisible goods. We extend earlier models’ definitions of substitutability to settings in which each agent can be both a buyer in some transactions and a seller in others, and show that all these definitions are equivalent. We then introduce a new class of substitutable preferences that allows us to model intermediaries with production capacity. We also prove that substitutability is preserved under economically important transformations such as trade endowments, mergers, and limited liability.
Stability and Competitive Equilibrium in Trading Networks
(joint with John W. Hatfield, Scott D. Kominers, Michael Ostrovsky, and Alexander Westkamp)
Journal of Political Economy, v. 121(5), October 2013, pp. 966-1005. - Online Appendix.
Abstract: We introduce a model in which agents in a network can trade via bilateral contracts. We find that when continuous transfers are allowed and utilities are quasi-linear, the full substitutability of preferences is sufficient to guarantee the existence of stable outcomes for any underlying network structure. Furthermore, the set of stable outcomes is essen- tially equivalent to the set of competitive equilibria, and all stable outcomes are in the core and are efficient. By contrast, for any domain of preferences strictly larger than that of full substitutability, the existence of stable outcomes and competitive equilibria cannot be guaranteed.
The Intellectual Influence of Economic Journals: Quality versus Quantity
(joint with László Á. Kóczy)
Economic Theory, v.52(3), April 2013, pp. 863-884.
Abstract: The evaluation of scientific output has a key role in the allocation of research funds and academic positions. Decisions are often based on quality indicators for academic journals and over the years a handful of scoring methods have been proposed for this purpose. Discussing the most prominent methods (de facto standards) we show that they do not distinguish quality from quantity at article level. The systematic bias we find is analytically tractable and implies that the methods are manipulable. We introduce modified methods that correct for this bias, and use them to provide rankings of economic journals. Our methodology is transparent; our results are replicable.
Consistency in One-Sided Assignment Problems
(joint with Bettina E. Klaus)
Social Choice and Welfare, v.35(3), September 2010, pp. 415-433.
Abstract: One-sided assignment problems combine important features of two well-known matching models. First, as in roommate problems, any two agents can be matched and second, as in two-sided assignment problems, the division of payoffs to agents is flexible as part of the solution. We take a similar approach to one-sided assignment problems as Sasaki (Int J Game Theory 24:373–397, 1995) for two-sided assignment problems, and we analyze various desirable properties of solutions including consistency and weak pairwise-monotonicity. We show that for the class of solvable one-sided assignment problems (i.e., the subset of one-sided assignment problems with a non-empty core), if a subsolution of the core satisfies [Pareto indifference and consistency] or [invariance with respect to unmatching dummy pairs, continuity, and consistency], then it coincides with the core (Theorems 1 and 2). However, we also prove that on the class of all one-sided assignment problems (solvable or not), no solution satisfies consistency and coincides with the core whenever the core is non-empty (Theorem 4). Finally, we comment on the difficulty in obtaining further positive results for the class of solvable one-sided assignment problems in line with Sasaki's (1995) characterizations of the core for two-sided assignment problems.
Book chapters
Generalized Matching: Contracts and Networks
(joint with John W. Hatfield, Ravi Jagadeesan, Scott Kominers, Michael Ostrovsky, Alexander Teytelboym and Alexander Westkamp)
In Online and Matching-Based Market Design, Cambridge University Press, 2023, Chapter 14, pp. 303-323,
edited by F. Echenique, N. Immorlica, and V. Vazirani
For the complete PDF of the book, click here (the password is “OMBMD_CUP”, also printed on the copyright page).
Case studies
Birchal: Equity Crowdfunding in Australia
(joint with Scott Kominers)
Harvard Business School Case 9-820-116 (2021)
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