Publications des chercheurs de PSE

Individuals interact through social media networks by posting contributions, comments and the like. These actions entail complementarities and generate spillovers. A social media carefully designs its platform, often with the objective of increasing users' activity. Here I study visibility strategies, which promote some individuals by making their contributions more visible than others'. Under some specifications, optimal strategies are simple, making visible the individuals whose total impact (total number of followers for example) is maximal. Comparisons with other targeting strategies are discussed.

In a variety of systems, in particular in a financial system, entities hold liabilities on each other. The reimbursement abilities are intertwined, thereby potentially generating coordination failures and cascades of defaults calling for orderly resolution. With a single indebted firm, a bankruptcy law organizes such an orderly resolution. With cross-liabilities, a resolution rule should be defined at the system level to account for all those affected, directly or indirectly. This paper investigates such rules assuming their primary goal is to avoid defaults on creditors external to the system, say banks’ defaults on customers’ deposits. I define and characterize the constrained-proportional rule building on two approaches: the minimization of an inequality measure on the reimbursements (made and received) and the axiomatization through desirable properties.

In a cooperative game, coalitions are the fundamental behavioral units. Stable outcomes (in the core) are those blocked by no coalition. This paper has two objectives. First, building on the notion of intermediate preferences indexed by a median graph, I unify and extend previous results on the existence of stable outcomes in simple games. Second, I review how and when the core approach applies in more general settings and may help to predict the stable splitting of a whole group into disjoint coalitions.

We study competition between European Union’s Central CounterParties (CCPs) on the credit default swap (CDS) market. Using data on market shares, we show that CCPs have a monopoly for single-name CDSs and compete on indices along various dimensions. Using transactions data, we focus on the major dealers who alternatively clear their transactions on the two main CCPs. Estimating their choice of CCP reveals that fees, CCPs’ robustness and activity, dealers’ risk, and market volatility are significant. Dealers’ positions indicate that saving on collateral costs is secondary relative to the benefits of dual membership and quality.

In a cooperative game, coalitions are the fundamental behavioral units. Stable outcomes (in the core) are those blocked by no coalition. This paper has two objectives. First, building on the notion of intermediate preferences indexed by a median graph, I unify and extend previous results on the existence of stable outcomes in simple games. Second, I review how and when the core approach applies in more general settings and may help to predict the stable splitting of a whole group into disjoint coalitions

This paper analyzes the strategy of a monopolistic digital platform serving users from two jurisdictions with different corporate tax rates. We consider two profit-splitting rules, Separate Accounting and Formula Apportionment based on the number of users in the two jurisdictions. We show that, even in the absence of transfer pricing, the platform shifts profit from the high-tax to the low-tax jurisdiction exploiting network externalities under Separate Accounting and manipulating the apportionment key under Formula Apportionment. In order to shift profit, the platform distorts prices and quantities. Under Separate Accounting, the direction of the distortions depends on the sign of the externalities. We use a numerical simulation to show that the ranking of fiscal revenues under the two regimes differs in the two jurisdictions: The high-tax jurisdiction prefers Separate Accounting to Formula Apportionment, whereas the low-tax jurisdiction prefers Formula Apportionment to Separate Accounting.

New regulations promote the role of Central Counter-Parties as insurers of counterparty risk to stabilize derivative markets. Most CCPs are for-profit institutions, competing for profits and market shares. Whether competition is harmful or beneficial to efficiency and financial stability is debatable, leading to different positions in the US and the EU. Assessing the impact of competition between CCPs is complex because of the many dimensions involved in their policies and the heterogeneity of their potential users, ranging from main intermediaries (the dealers) to final clients. We first review the business model of CCPs and illustrate the dimensions on which CCPs compete by gathering EU data on CCPs, their scopes, their clients and members. We then focus on the clearing of CDS by providing an empirical analysis of on the choices of CCPs by the main dealers.

In a variety of situations, entities in a system, for example firms in the financial sector, hold liabilities on each other. The reimbursement abilities are intertwined, thereby potentially generating coordination failures and a cascade of defaults calling for interventions. Interventions can be discretionary or designed by rules such as bankruptcy laws. Bankruptcy laws, however, manage the default of a single firm towards its creditors, without considering all those that could be affected indirectly by the resolution. To account for these indirect effects, resolution rules should be defined at the system level. This paper investigates such rules, assuming that the primary goal of the resolution is to avoid defaults on external debts, say, banks' defaults on deposits. Focusing on the proportionality principle, it defines and characterizes the constrained-proportional rule, building on two approaches: the minimization of an inequality measure of the reimbursements (made and received) and the axiomatization through desirable properties.

In over-the-counter markets for assets, such as bonds and securitizations, large volumes can be split into smaller pieces and gradually sold to several final investors with the intermediation of multiple dealers. This paper proposes a model to study this process, called asset dissemination. A dealer buys several units of an asset from a customer and then sells some units to the dealer’s customers and to a second dealer, who sells to the second dealer’s customers and to a third dealer, and so on. The extent of dissemination is measured by the number of dealers involved and the total customer demand served. We show that asymmetric information on customer demand hinders both dimensions of dissemination. We also study how the quantity to disseminate and the dealers’ funding costs impact dissemination and the prices and quantities in interdealer transactions. This paper was accepted by Gustavo Manso, finance.

In the last years, there has been a shift toward more private financing of higher education in many countries. At the same time, student mobility has substantially increased. This paper analyzes in a two-region model the impact of student mobility on region-specific higher education quality with private funding. Individuals decide whether and where to study based on their individual ability and the implemented quality. We show that mobility of students affects educational quality in very differ-ent ways depending on the probability of return migration. With full return migra-tion, quality is optimally provided which is in stark contrast to the underprovision result in the case of tax financing. On the contrary, low return migration and thus more competition for students countervail the efficient provision of quality and result in too little differentiated levels or too high symmetric levels. This is in line with the overprovision result with tax financing.

This paper proposes an analysis of strategic communication on platforms by candidates during an electoral campaign. A candidate's platform in a (possibly) multidimensional policy space is fixed, but is imperfectly known by voters. A candidate strategically decides the emphasis he puts on the various issues, and thus the precision of the information he conveys to voters on his position on each issue. We show that if voters are fully rational, then all the relevant information is revealed at equilibrium, whatever the candidate's true position. We then study a model of boundedly rational voters, who take at face value the messages sent by the politicians, without being able to decipher their strategies. If voters are boundedly rational in this sense, a politician will not transmit all the relevant information; his communication strategy will depend on both the prior in the electorate and his true positions (unknown to the electorate). In particular, we show that candidates address all issues with positive probability, but tend to talk more often on issues on which they are a priori congruent with the representative voter, thereby providing a “nuanced” version of Petrocik's “issue ownership theory”.

Due to computing and communication facilities, formal procedures, often referred to as 'al-gorithms', are now extensively used in public, economic and social areas. These procedures, currently at the forefront of criticisms, share some features with mechanisms as defined by economists, following Hurwicz. My aim is to investigate these relationships and to discuss the risks due to the power of algorithms.