Professor, Department of Economics, Sciences Po
Research Fellow at the Center for Economic Policy Research (CEPR).
Member of the Editorial Board of the Review of Economic Studies
Associate Editor at the American Economic Review

Fields:

[CV]

I have been awarded an ERC Consolidator Grant for my project Information and Misinformation Economics: Design, Manipulations and Countermeasures (IMEDMC).

Active Working Papers

Score-Based Mechanisms, Abstract: We propose a mechanism design framework that incorporates both soft information, which can be freely manipulated, and semi-hard information, which entails a cost for falsification. The framework captures various contexts such as school choice, public housing, organ transplant and manipulations of classification algorithms. We first provide a canonical class of mechanisms for these settings. The key idea is to treat the submission of hard information as an observable and payoff-relevant action and the contractible part of the mechanism as a mapping from submitted scores to a distribution over decisions (a score-based decision rule). Each type report triggers a distribution over score submission requests and a distribution over decision rules. We provide conditions under which score-based mechanisms are without loss of generality. In other words, situations under which the agent does not make any type reports and decides without a mediator what score to submit in a score-based decision rule. We proceed to characterize optimal approval mechanisms in the presence of manipulable hard information. In several leading settings optimal mechanisms are score-based (and thus do not rely on soft information) and involve costly screening. The solution methodology we employ is suitable both for concave cost functions and quadratic costs and is applicable to a wide range of contexts in economics and in computer science. This version: March 2024 with Vasiliki Skreta, 2024.
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Fraud-proof Non-market Allocation Mechanisms, Abstract: We study the optimal design of fraud-proof allocation mechanisms without transfers. An agent's eligibility relies on a score reflecting social value, but gaming generates misallocations, mistrust, unfairness and other negative externalities. We characterize optimal allocation rules that are immune to gaming under two classes of gaming technologies. We examine the impact of demographic changes on allocations within and across identifiable groups, while accounting for resource and quota constraints. Fraud-proof allocation rules enhance fairness and trust in allocation systems at the cost of some allocative efficiency. This version: March 2024 with Vasiliki Skreta, 2024.
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Non-Market Allocation Mechanisms: Optimal Design and Investment Incentives, Abstract: We study how to optimally design mechanisms for allocating scarce resources, accounting for agents’ investment incentives. A principal wishes to allocate a resource of homogeneous quality, such as seats in a university, to a heterogeneous population of agents. She commits ex-ante to a possibly random allocation rule that depends on a one-dimensional characteristic of the agents that she intrinsically values, but does not have access to monetary transfers. Agents have a strict preference to be allocated the resource and may undertake a costly investment to improve their characteristic before it is revealed to the principal. We show that while random allocation rules have the effect of encouraging investment, especially at the top of the characteristic distribution, deterministic pass-fail allocation rules, such as exams with a pass grade, prove to be optimal. This version: November 2022 with Victor Augias, 2022.
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Communication via Third Parties, Abstract: A principal designs an information structure and chooses transfers to an agent that are contingent on the action of a receiver. The principal faces a trade-off between, on the one hand, designing an information structure maximizing non-monetary payoffs, and on the other hand, minimizing the information rent that must be conceded to the agent in order to implement the information structure which the principal designed. We examine how this trade-off shapes communication. Our model can be applied to study the relationship between, e.g.: political organizations and the public relations companies that campaign on their behalf, firms and the companies marketing their products, consultancies and the analysts they employ. This version: March 2021 with Jacopo Bizzotto and Adrien Vigier, 2021.
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Information Design with Agency, Abstract: We consider a general information design problem in which the task of running a procedure generating information for a continuation game is performed by an agent. A moral hazard problem therefore emerges in which the principal faces a trade-off between generating information that is persuasive in the continuation game, and efficiently incentivizing the agent to comply with the procedure designed. Standard concavification techniques do not apply in this environment. We provide a general methodology to tackle such problems, and examine the way in which moral hazard affects the optimal procedure of the principal. This version: February 2020 with Jacopo Bizzotto and Adrien Vigier, 2020.
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Published or Accepted Papers

Test Design under Falsification, Abstract: We study the optimal design of tests with manipulable inputs. Tests take a unidimensional state of the world as input, and output an informative signal to guide a receiver's approve or reject decision. The receiver wishes to only approve states that comply with her baseline standard. An agent with a preference for approval can covertly falsify the state of the world at a cost. We characterize receiver-optimal tests and show they rely on productive falsification by compliant states. They work by setting a more stringent operational standard, and granting noncompliant states a positive approval probability to deter them from falsifying to the standard. We also study how falsification-detection technologies improve optimal tests. They allow the designer to build an implicit cost of falsification into the test, in the form of signal devaluations. Exploiting this channel requires enriching the signal space. This version: November 2021 with Vasiliki Skreta, Econometrica, 2022, 90, 3, 1109-1142.
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Altruism and Risk Sharing in Networks, Abstract: We provide the first analysis of the risk sharing implications of altruism networks. Agents are embedded in a fixed network and care about each other. We explore whether altruistic transfers help smooth consumption and how this depends on the shape of the network. We find that altruism networks have a first-order impact on risk. Altruistic transfers generate efficient insurance when the network of perfect altruistic ties is strongly connected. We uncover two specific empirical implications of altruism networks. First, bridges can generate good overall risk sharing and, more generally, the quality of informal insurance depends on the average path length of the network. Second, large shocks are well-insured by connected altruism networks. By contrast, large shocks tend to be badly insured in models of informal insurance with frictions. We characterize what happens for shocks that leave the structure of giving relationships unchanged. We further explore the relationship between consumption variance and centrality, correlation in consumption streams across agents and the impact of adding links. This version: May 2020 with Renaud Bourlès and Yann Bramoullé, Journal of the European Economic Association, 2021, 19, 3.
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Evidence Reading Mechanisms, Abstract: We study implementation with privately informed agents who can produce evidence. We characterize social choice functions that are implementable by mechanisms that are robust to the designer's commitment power, and simply apply the social choice function to a reading of the evidence. In this class of mechanisms, our results provide conditions on the evidence structure such that (i) a function that is implementable with transfers is also implementable with evidence but no transfer, (ii) under private value, the efficient allocation is implementable with budget balanced and individually rational transfers, and (iii) in single-object auction and bilateral trade environments with interdependent values, the efficient allocation is implementable with budget balanced and individually rational transfers. This version: December 2018 with Frederic Koessler, Social Choice and Welfare, 2019, 52, 194, 1-23.
(formerly circulated under the title: Evidence Based Mechanisms)
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Communication with Evidence in the Lab, Abstract: We study a class of sender-receiver disclosure games in the lab. Our experiment relies on a graphical representation of sender's incentives in these games, and permits partial disclosure. We use local and global properties of the incentive graph to explain behavior and performance of players across different games. Sender types whose interests are aligned with those of the receiver fully disclose, while other types use vague messages. Receivers take the evidence disclosed by senders into account, and perform better in games with an acyclic graph. Senders perform better in games with a cyclic graph. The data is largely consistent with a non-equilibrium model of strategic thinking based on the iterated elimination of obviously dominated strategies. This version: September 2018 with Jeanne Hagenbach, Games and Economic Behavior, 2018, 112, 139-165.
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Altruism in Networks, Abstract: We provide the first analysis of altruism in networks. Agents are embedded in a fixed network and care about the well-being of their network neighbors. Depending on incomes, they may provide financial support to their poorer friends. We study the Nash equilibria of the resulting game of transfers. We show that equilibria maximize a concave potential function. We establish existence, uniqueness of equilibrium consumption and generic uniqueness of equilibrium transfers. We characterize the geometry of the network of transfers and highlight the key role played by transfer intermediaries. We then study comparative statics. A positive income shock to an individual benefits all. For small changes in incomes, agents in a component of the network of transfers act as if they were organized in an income-pooling community. A decrease in income inequality or expansion of the altruistic network may increase consumption inequality. This version: November 2016 with Renaud Bourlès and Yann Bramoullé, Econometrica, 2017, 85, 2, 675-689.
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Interim Bayesian Persuasion: First Steps, Abstract: This paper makes a first attempt at building a theory of interim Bayesian persuasion. I work in a minimalist model where a low or high type sender seeks validation from a receiver who is willing to validate high types exclusively. After learning her type, the sender chooses a complete conditional information structure for the receiver from a possibly restricted feasible set. I suggest a solution to this game that takes into account the signaling potential of the sender's choice. Last version: January 2014 American Economic Review: Papers & Proceedings, 2014, 104, 5.
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Certifiable Pre-Play Communication: Full Disclosure, Abstract: This article asks when communication with certifiable information leads to complete information revelation. We consider Bayesian games augmented by a pre-play communication phase in which announcements are made publicly. We first characterize the augmented games in which there exists a fully revealing sequential equilibrium with extremal beliefs (i.e., any deviation is attributed to a single type of the deviator). Next, we define a class of games for which existence of a fully revealing equilibrium is equivalent to a richness property of the evidence structure. This characterization enables us to provide different sets of sufficient conditions for full information disclosure that encompass and extend all known results in the literature, and are easily applicable. We use these conditions to obtain new insights in persuasion games with multidimensional types, games with strategic complementarities, and voting with deliberation. Last version: December 2013 with Jeanne Hagenbach and Frederic Koessler, Econometrica, 2014, 82, 3, 1093-1131.
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Choosing Choices: Agenda Selection with Uncertain Issues, Abstract: We study selection rules: voting procedures used by committees to choose whether to place an issue on their agenda. At the selection stage of the model, committee members are uncertain about their final preferences. They only have some private information about these preferences. We show that voters become more conservative when the selection rule itself becomes more conservative. The decision rule has the opposite effect. We compare these voting procedures to the designation of an agenda setter among the committee, and to a utilitarian social planner with all the ex interim private information. Last version: July 2012. with Raphael Godefroy, Econometrica, 2013, 81, 1, 221-253.
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A Note on the Tight Simplification of Mechanisms, Abstract: Paul Milgrom (2010) proposes to simplify mechanisms by restricting their message space. When doing so, it is important not to create new equilibria. A weakly tight simplification is one that does not create new Nash equilibria, a tight simplification is one that does not create new ε-Nash equilibria. This note offers characterizations of tightness. When the preference domain is that of continuous utility functions on the outcome space, the two notions are equivalent, and are also equivalent to the outcome closure property of Milgrom (2008). Last version: August 2010 Economics Letters, 2011.
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Inactive Working Papers

A Proof of Blackwell's Theorem, Abstract: This note gives a new proof of Blackwell's celebrated result. The result is a bit stronger than the classical version since the action set and the prior are fixed, and only the utility of the decision maker varies. I show directly that a decision maker has access to a larger set of joint distributions over actions and states of the world if and only if her information improves in the garbling order. This version: November 2017 2017.

Complicating to Persuade?, Abstract: This paper addresses a common criticism of certification processes: that they simultaneously generate excessive complexity, insufficient scrutiny and high rates of undue validation. We build a model of persuasion in which low and high types pool on their choice of complexity. A natural criterion based on forward induction selects the high-type optimal pooling equilibrium.When the receiver prefers rejection ex ante, the sender simplifies her report. When the receiver prefers validation ex ante, however, more complexity makes the receiver less selective, and we provide sufficient conditions that lead to complexity inflation in equilibrium. This version: February 2012 with Delphine Prady, 2012.
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Competing with Equivocal Information, Abstract: This paper studies strategic disclosure between multiple senders and a single receiver. The senders are competing for prizes awarded by the receiver. They decide whether to disclose a piece of information that is both verifiable and equivocal (it can influence the receiver both ways). Then the standard unraveling argument breaks down: if the commonly known probability that her information is favorable is sufficiently high, a single sender never discloses. Competition restores full disclosure only if some of the senders are sufficiently unlikely to have favorable information. When the senders are uncertain about each other's strength, however, all symmetric equilibria approach full disclosure as the number of candidates increases. This version: July 2012 2012.
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