
James Schummer
Research Page
Contact Information
James Schummer
MEDS, Kellogg School of Management
Northwestern University
Evanston, IL 60208–2009, USA

Phone: 8474915151
Fax: 8474671220
MEDS Dept.: 8474913603

Curriculum Vitae (pdf)
Work in Progress
 “Influencing Waiting Lists.”
 Download Waiting.pdf.
 Abstract:
Scarce goods (donor organs, public housing, etc.) are often allocated through waiting lists,
especially when monetary transfers are undesirable.
Arriving objects are offered to priorityordered agents who may
defer the object to the next agent in line in order to wait for a better one.
We consider the welfare implications of arbitrarily influencing such deferral decisions (by force, by “nudging,” etc.).
When agents are patient, uninfluenced (equilibrium) behavior is Paretodominant; this conclusion strengthens as agents’ riskaversion increases.
When riskneutral agents are impatient, however, influence results in a welfare tradeoff between earlier and later agents in the queue.
The results have implications for the “organ spoilage” problem in waiting lists for donor organs,
where useful lowerquality organs spoil in the time that it takes to process the deferrals by agents early in the queue.
Removing the right to defer such organs appears to solve the wastage problem by increasing utilization.
But for some parameters (e.g. extremely high riskaversion) such solutions could paradoxically lower the welfare of some agents
it is intended to help. Fortunately the parameters that result in this phenomenon appear to be atypical in real world settings.
 Preliminary version featured in Kellogg Insight, Dec 2016.
 “Revenue from Matching Platforms” (with Philip Marx).
 Download the working paper (PDF) (version: February 2019).
 Abstract:
We consider the pricing problem of a matchmaking platform where heterogeneous agents create exclusive, stable matchings and pay matchcontingent fees.
Absent prices, agents on the short side of such markets capture relatively greater surplus than those on the long side (Ashlagi et al., 2017).
Nevertheless we show that this need not induce the platform to bias its price allocation on the basis of market imbalance:
with independently drawn preferences, optimal price allocation decisions are independent of market size or imbalance.
Larger markets induce higher price levels, leading to price increases for both sides of the market;
consequently the “cost of stability” imposed on the platform becomes negligible.
In contrast, preference correlation leads to price allocation bias
that depends on an interaction between market imbalance and preference correlation;
changes in market imbalance lead to opposing price changes for the two sides.
This interaction is a novel effect that arises from the exclusivity of interactions in a twosided market.
 “Sequential Preference Revelation in Incomplete Information Settings” (with Rodrigo Velez).
 Download the working paper (PDF) (version: September 2019).
 Download the online appendix (PDF).
 Abstract:
Strategyproof allocation rules incentivize truthfulness in simultaneous move games, but real world mechanisms sometimes elicit preferences sequentially.
Surprisingly, even when the underlying rule is strategyproof and nonbossy, sequential elicitation can yield equilibria where agents have a strict incentive to be untruthful.
This occurs only under incomplete information, when an agent anticipates that truthful reporting would signal false private information about others’ preferences.
We provide conditions ruling out this phenomenon, guaranteeing all equilibrium outcomes to be welfareequivalent to truthful ones.
 “The Role of Characterizations in Market Design” (with Shigehiro Serizawa).
 “Voting with Money” (with Rakesh V. Vohra).
 This is some old work. Preliminary results are available upon request.
Published Papers
 “Incentives in Landing Slot Problems” (with Azar Abizada).
 Journal of Economic Theory (2017) 170, 29–55.
 View at doi.org/10.1016/j.jet.2017.04.003.
 Online appendix.
 Working paper version (Jan. 2017, includes online appendix).
 Abstract:
During weatherinduced airport congestion, landing slots are reassigned based on flights’ feasible arrival times and cancelations.
We consider the airlines’ incentives to report such information and to execute cancelations, creating positive spillovers for other flights.
We show that such incentives conflict with Paretoefficiency, partially justifying the FAA’s nonsolicitation of delay costs.
We provide mechanisms that, unlike the FAA’s current mechanism, satisfy our incentive properties to the greatest extent
possible given the FAA’s own design constraints.
Our mechanisms supplement Deferred Acceptance with a “selfoptimization” step accounting for each airline’s
granted right to control its assigned portion of the landing schedule.
 “Assignment of Arrival Slots” (with Rakesh V. Vohra).
 American Economic Journal: Microeconomics (2013) 5:2, 164–185.
 Download: slotsAEJM.pdf.
 View at AEAweb.
 Abstract:
During inclement weather, the FAA reassigns vacated airport landing slots within a certain time interval.
We consider this mechanism design problem when a preexisting landing schedule defines certain
property rights for the airlines.
This particular problem has been analyzed from an operational perspective,
where the motivation for the FAA’s current mechanism—the Compression Algorithm—rests
on incentives and property rights.
This paper appears to be the first to rigorously formalize these two notions for this application.
Our results show that the Compression Algorithm satisfies a certain form of incentive compatibility
but fails a certain interpretation of property rights.
We then provide an example of a mechanism that satisfies both conditions;
proofs of this use a different but related matching model.
Neither mechanism, however, would always gives airlines the incentive to vacate unusable landing slots if
airlines can prevent the slot’s inclusion in either of these trading algorithms.
 Featured in Kellogg Insight, May 2012.
 “An Ascending Vickrey Auction for Selling Bases of a Matroid”
(with Sushil Bikhchandani, Sven de Vries, and Rakesh V. Vohra).
 Operations Research (2011) 59:2, 400–413.
 Download: MatroidOR2011.pdf. Also see the eCompanion.
 View at Informs Online.
 Abstract:
Consider selling bundles of indivisible goods to buyers
with concave utilities that are additively separable in money and goods.
We propose an ascending auction for the case when the seller is
constrained to sell bundles whose elements form a basis of a
matroid. It extends easily to polymatroids.
Applications include scheduling (Demange, Gale, and Sotomayor, 1986),
allocation of homogeneous goods (Ausubel, 2004),
and spatially distributed markets (Babaioff, Nisan, and Pavlov, 2004).
Our ascending auction induces buyers to bid
truthfully, and returns the economically efficient basis.
Unlike other ascending auctions for this environment,
ours runs in pseudopolynomial or polynomial time.
Furthermore we prove the impossibility of
an ascending auction for nonmatroidal independence setsystems.
 “Credible Deviations from Signaling Equilibria” (with Péter Esö).
 International Journal of Game Theory (2009) 38:3, 411–430.
 View at SpringerLink.
 Download final version: CDC.pdf.
 Our final “working paper version”
contains more information plus extra discussion about refinements that does not appear
in the published version. For those interested in a deeper reading on this topic, within
the context of the refinements literature, I recommend reading this preeditorialized version.
In the past we have received positive comments about the helpfulness of this version’s extra discussion.
 The supplemental appendix proves some claims
and provides more examples.
 Abstract:
In SenderReceiver games with costly signaling, some equilibria are
vulnerable to deviations which could be “unambiguously” interpreted by
the Receiver as coming from a unique set of possible Sendertypes.
The vulnerability occurs when the types in this set are the ones who
gain from the deviation, regardless of the posterior beliefs the
Receiver forms over that set.
We formalize this idea and use it to characterize a unique equilibrium
outcome in two classes of games.
First, in monotonic signaling games, only the Riley outcome is immune
to this sort of deviation.
Our result therefore provides a plausible story behind the selection
made by Cho and Kreps’ (1987) D1 criterion on this class of games.
Second we examine a version of Crawford and Sobel’s (1982) model but
with costly signaling and finite type sets, where standard refinements have no effect.
We show that only a Rileylike separating equilibrium is immune to these deviations.

“Mechanism Design without Money” (with Rakesh V. Vohra).
 This is a chapter in the book
Algorithmic
Game Theory (Nisan, Roughgarden, Tardos, Vazirani, eds.), Cambridge University Press, 2007.
 Update: Want a free PDF of the entire book? Go to the
publisher’s
catalog page and click on the Resources button half way down. Enjoy!
 Abstract:
Despite impossibility results on general domains, there are some classes of
situations in which there exist interesting dominantstrategy mechanisms. While
some of these situations (and the resulting mechanisms) involve the transfer of
money, we examine some that do not. Specifically, we analyze: problems where
agents have singlepeaked preferences over a 1dimensional public policy
space; problems where agents can trade/consume a single, indivisible private
good; and problems where agents must match with each other.
 “On Ascending Vickrey Auctions for Heterogeneous Objects” (with
Sven de Vries and Rakesh V. Vohra).
 Journal of Economic Theory (2007) 132:1, 95–118.
 View at ScienceDirect.
 Download the prepublication version.
 Abstract:
We construct an ascending auction for heterogeneous objects
by applying a primaldual algorithm to a linear program that
represents the efficientallocation problem for this setting.
The auction assigns personalized prices to bundles, and asks bidders
to report their preferred bundles in each round.
A bidder’s prices are increased when he belongs to a “minimally undersupplied” set
of bidders. We consider this concept to be the natural generalization
of an “overdemanded” set of objects, introduced by Demange et al. (1986)
for the onetoone assignment problem.
Under a submodularity condition, the auction implements the Vickrey–Clarke–Groves
outcome; we show that this type of condition is somewhat necessary to do so.
When classifying the ascendingauction literature in terms of their underlying algorithms,
our auction fills a gap in that literature.
We relate our results to the recent work of Ausubel and Milgrom (2002).
 Try out a
javascript applet
which executes the auction algorithm derived in the paper!
 “Almostdominant Strategy Implementation”
 Games and Economic Behavior (2004) 48, 154–170.
 View at ScienceDirect.
 Download the prepublication version.
 Abstract:
We examine the consequences of relaxing strategyproofness
(a form of dominant strategy implementation) by allowing
instances of “small” gains from manipulation.
In 2agent exchange economies, this relaxation is shown to have
a discontinuous effect on the range of efficient rules.
This demonstrates a type of nonrobustness in previous
impossibility results.
When small gains are measured with respect to a single good,
we show that a particular rule is, unambiguously,
most equitable among all efficient rules satisfying the relaxed condition.

“Bribing and Signaling in Secondprice Auctions” (with
Péter Esö)
 Games and Economic Behavior (2004) 47, 299–324.
 View at ScienceDirect.
 Download the prepublication version.
 The
Working
Paper version (Oct. 2002) contains related results.
 We have some unpublished
supplemental
notes on variations of the model in this paper.
 Abstract:
We examine whether a twobidder, secondprice auction for a single
good (with private, independent values) is immune to a simple form
of collusion, where one bidder may bribe the other to commit to
stay away from the auction (i.e. submit a bid of zero).
In either of two cases—where the potential bribe is fixed or
allowed to vary—the only robust equilibria involve bribing.
In the fixedbribe case, there is a unique such equilibrium.
In the variable bribes case, all robust equilibria involve low bribertypes
revealing themselves through the amount they offer, while all high
types offer the same bribe; only one such equilibrium is continuous.
Bribing in all cases causes inefficiency.

“Auctions for Procuring Options” (with Rakesh V. Vohra)
 Operations Research (2003) 51, 41–51.
 View at INFORMS.
 Abstract:
We examine the mechanism design problem for a single buyer to
procure purchaseoptions for a homogeneous good when that buyer is required
to satisfy an unknown future demand.
Suppliers have 2dimensional types in the form of commitment costs
and production costs.
The efficient schedule of options depends on the distribution of demand.
To implement an efficient outcome, we introduce a class of
mechanisms which are essentially pivotal mechanisms
(Vickrey–Clarke–Groves) with respect to the expected costs of
the suppliers.
We show that the computational task of running such mechanisms is
not burdensome.
Our discussion uses electricity markets as an example.

“Linear Programming and Vickrey Auctions” (with Sushil Bikhchandani,
Sven de Vries, and Rakesh V. Vohra)
 In
Mathematics
of the Internet: Eauction and Markets, an IMA Volume in
Mathematics and its Applications, Dietrich and Vohra, ed., Springer, 2002.
 Abstract:
The Vickrey sealed bid auction occupies a central place in auction theory
because of its efficiency and incentive properties.
Implementing the auction requires the auctioneer to solve n+1 optimization
problems, where n is the number of bidders.
In this paper we survey various environments (some old and some new)
where the payments bidders make under the Vickrey auction correspond to
dual variables in certain linear programs.
Thus, in these environments, at most two optimization
problems must be solved to determine the Vickrey outcome.
Furthermore, primaldual algorithms for some of these linear
programs suggest ascending auctions that implement the Vickrey outcome.

“Strategyproof Location on a Network” (with Rakesh V. Vohra)
 Journal of Economic Theory (2002) 104, 405–428.
 View at ScienceDirect.
 Download the prepublication version.
 Abstract:
We consider rules that choose a location on a graph (e.g. a
road network) based on agents’ singlepeaked preferences.
First, we characterize the class of strategyproof, onto rules
when the graph is a tree.
Such a rule is based on a collection of generalized
median voter rules (Moulin, 1980) satisfying a consistency condition.
Second, we characterize such rules for graphs containing cycles.
We show that while such a rule is not necessarily dictatorial,
the existence of a cycle grants some agent
an amount of decisive power, unlike the case of trees.
Rules for this case can be described
in terms of a subclass of such rules for trees.
Journal of Economic Literature Classification Numbers: C72, D78.
 “Constrained Egalitarianism: A New Solution for Claims Problems” (with Y. Chun and W. Thomson)
 Seoul Journal of Economics (2001) 14, 269–298.
 Download.
 Abstract:
We propose a new rule to solve claims problems (O’Neill 1982) and show that this rule
is best in achieving certain objectives of equality. We present three theorems describing
it as the most “egalitarian” among all rules satisfying two minor requirements,
“estatemonotonicity” and “the midpoint property.”
We refer to it as the “constrained egalitarian” rule.
We show that it is consistent and give a parametric representation of it.
We also define several other rules and relate all of them to the
rules that have been most commonly discussed in the literature.
Journal of Economic Literature Classification Numbers: D63, D70.
 “Manipulation through Bribes”
 Journal of Economic Theory (2000) 91, 180–198.
 This paper can be
downloaded.
 View at
ScienceDirect.
 Abstract:
We consider allocation rules that choose both an outcome
and transfers, based on the agents’ reported valuations of the outcomes.
Under a given allocation rule, a bribing situation exists when
agent j could pay agent i to misreport his valuations, resulting
in a net gain to both agents.
A rule is bribeproof if such opportunities never arise.
The central result is that when a bribeproof rule is used,
the resulting payoff to any one agent is a continuous
function of any other agent’s reported valuations.
We then show that on connected domains of valuation functions,
if either the set of outcomes is finite or
each agent’s set of admissible valuations is smoothly connected,
then an agent’s payoff is a constant function of other agents’
reported valuations.
Finally, under the additional assumption of a standard domainrichness
condition, we show that a bribeproof rule must be a constant function.
The results apply to a very broad class of economies.
 “Eliciting Preferences to Assign Positions and Compensation”
 Games and Economic Behavior (2000) 30, 293–318.
 View at
ScienceDirect.
 Abstract:
We describe strategyproof rules for economies where an agent is assigned a
position (e.g., a job) plus some of a divisible good. For the
2agent–2position case we derive a robust characterization. For the
multiagentposition case, many “arbitrary” such rules exist, so we consider
additional requirements. By also requiring coalitional strategyproofness or
nonbossiness, the range of a solution is restricted to the point that such
rules are not more complex than those for the ShapleyScarf housing model (no
divisible good). Third, we show that essentially only constant solutions are
immune to manipulations involving “bribes.” Finally, we demonstrate a
conflict between efficiency and strategyproofness. The results extend to
models (without externalities) in which agents share positions
 “Strategyproofness versus Efficiency for Small Domains of Preferences over Public Goods”
 Economic Theory (1999) 13, 709–722.
 See
this
paper at SpringerLink.
 Abstract:
It has long been known that when agents have von Neumann–Morgenstern
preferences over lotteries, there is an incompatibility between
strategyproofness and efficiency (Gibbard (1973), Hylland (1980))—a solution
satisfying those properties must be dictatorial. We strengthen this result
by showing that it follows from the same incompatibility on a series of much
smaller domains of preferences.
Specifically, we first show the incompatibility to hold on our
smallest domain, in which two agents are restricted to have linear
preferences over one private good and one public good produced from the
private good (Kolm triangle economies). This result then implies the same
incompatibility on increasingly larger domains of preferences, ending finally
with the class of von Neumann–Morgenstern preferences over lotteries.
 “Strategyproofness versus Efficiency on Restricted Domains of Exchange Economies”
 Social Choice and Welfare (1997) 14, 47–56.
 See
this
paper at SpringerLink.
 Abstract:
Strategyproofness has been shown to be a strong property, particularly on
large domains of preferences. We therefore examine the existence of
strategyproof and efficient solutions on restricted, 2person domains of
exchange economies. On the class of 2person exchange economies in which
agents have homothetic, strictly convex preferences we show, as Zhou (1991)
did for a larger domain, that such a solution is necessarily dictatorial. As
this proof requires preferences exhibiting high degrees of complementarity,
our search continues to a class of linear preferences. Even on this “small”
domain, the same negative result holds. These two results are extended to
many superdomains, including Zhou’s.
 “Two Derivations of the Uniform Rule and an Application to Bankruptcy”
(with William Thomson)
 Economics Letters (1997) 55, 333–337.
 View at
ScienceDirect.
 Abstract:
We consider the problem of allocating a single infinitely divisible commodity to agents with
singlepeaked preferences, and establish two properties of the rule that has played the
central role in the analysis of this problem, the uniform rule. Among the efficient allocations,
it selects (1) the one at which the difference between the largest amount received by any
agent and the smallest such amount is minimal, and (2) the one at which the variance of the
amounts received by all the agents is minimal. We also show that an important solution for
bankruptcy problems, the constrained equalaward solution, can be characterized by
analogous minimization exercises, subject to different constraints.
Unpublished Manuscripts
 “A Pedagogical Example of Nonconcavifiable Preferences”
(version: March 1998)
 Dissertation: “Strategyproof Allocation for Restricted Economic Domains”
(My Ph.D. dissertation, completed at the
University of Rochester in
1997, under the supervision of
William Thomson.)
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