Publications

Most of the information presented on this page have been retrieved from RePEc with the kind authorization of Christian Zimmermann
On inexact versions of a quasi-equilibrium problem: a Cournot duopoly perspectiveJournal articleE. L. Dias Júnior, P. J. S. Santos, A. Soubeyran and J. C. O. Souza, Journal of Global Optimization, 2023

This paper has two parts. In the mathematical part, we present two inexact versions of the proximal point method for solving quasi-equilibrium problems (QEP) in Hilbert spaces. Under mild assumptions, we prove that the methods find a solution to the quasi-equilibrium problem with an approximated computation of each iteration or using a perturbation of the regularized bifunction. In the behavioral part, we justify the choice of the new perturbation, with the help of the main example that drives quasi-equilibrium problems: the Cournot duopoly model, which founded game theory. This requires to exhibit a new QEP reformulation of the Cournot model that will appear more intuitive and rigorous. It leads directly to the formulation of our perturbation function. Some numerical experiments show the performance of the proposed methods.

The Academic Market and The Rise of Universities in Medieval and Early Modern Europe (1000–1800)Journal articleDavid de la Croix, Frédéric Docquier, Alice Fabre and Robert Stelter, Journal of the European Economic Association, pp. jvad061, 2023

We argue that market forces shaped the geographic distribution of upper-tail human capital across Europe during the Middle Ages, and contributed to bolstering universities at the dawn of the Humanistic and Scientific Revolutions. We build a unique database of thousands of scholars from university sources covering all of Europe, construct an index of their ability, and map the academic market in the medieval and early modern periods. We show that scholars tended to concentrate in the best universities (agglomeration), that better scholars were more sensitive to the quality of the university (positive sorting) and migrated over greater distances (positive selection). Agglomeration, selection, and sorting patterns testify to an integrated academic market, made possible by the use of a common language (Latin).

Entry-regulation and corruption: grease or sand in the wheels of entrepreneurship? Fresh evidence according to entrepreneurial motivesJournal articleMarcus Dejardin and Hélène Laurent, Small Business Economics, 2023

The relationship between entry-regulation, corruption, and entrepreneurship is controversial in the literature. Using a broad cross-country dataset to deepen the investigation, this paper distinguishes opportunity and necessity-motivated entrepreneurship in different development contexts. Corruption might grease the wheels of ineffective administrative machinery in developing countries with heavy entry-regulation. Yet, the marginal effect of corruption will generally be non-significant in other developing countries and in developed countries. Moreover, our results suggest that corruption deters opportunity-motivated entrepreneurship—the type of entrepreneurship that may contribute the most to productivity, economic growth, and development—in developed countries.

On portfolio frictions, asset returns and volatilityJournal articleAurélien Eyquem, Celine Poilly and Anna Belianska, European Economic Review, Volume 160, pp. 104623, 2023

We rationalize the observed short-run differences in corporate and long-term government bond yields in an financial-accelerator model with frictions that restrict changes in portfolio shares. We estimate the model on quarterly data for the Euro Area from 1999 to 2019, and show that the portfolio friction parameter is positive and significant. Portfolio frictions not only generate a time-varying wedge between the two returns that fits the data, but also raise the volatility of return differentials, and the precautionary motive of savers. As a result, the macroeconomic effects of uncertainty shocks are amplified by portfolio frictions.

The weakness of common job contactsJournal articleSofia Ruiz-Palazuelos, Maria Paz Espinosa and Jaromir Kovarik, EUROPEAN ECONOMIC REVIEW, Volume 160, pp. 104594, 2023

Many people obtain job information from friends and acquaintances. However, one factor influencing labor-market outcomes that is ignored in the literature is the presence of overlapping friendship circles in social networks. We find that overlapping friendship networks produce correlated information flows, resulting in an increased probability of two events: either receiving redundant job offers or receiving no job offers at all. Consequently, people with common contact networks exhibit worse employment prospects even if they have the same number of information providers and compete with the same number of people for vacancies. In quantitative terms, the impact of overlapping friendship circles rivals that of the number of direct contacts and contacts' contacts. This implies that the results in Calvo-Armengol (2004) only apply for networks where people's friends are neither connected nor have common contacts. Because overlapping friendship circles are a crucial aspect of strong relationships, our findings uncover an alternative mechanism behind "The Strength of Weak Ties"(Granovetter, 1973): their ability to maintain independence in job information flows. We further show that people with common job contacts earn lower incomes on average. However, conditional on being employed, their expected wage is higher because they can take advantage of the multiple job offers received by selecting the one with the highest pay.

Location games with referencesJournal articleGaëtan Fournier and Amaury Francou, Games and Economic Behavior, Volume 142, pp. 17-32, 2023

We study a class of location games where players want to attract as many resources as possible and pay a cost when deviating from an exogenous reference location. This class of games includes political competitions between policy-interested parties and firms' costly horizontal differentiation. We find that the introduction of reference locations simplifies the set of pure-strategy equilibrium to a unique candidate which has a strong property: at most four players, the two most-left and two most-right, deviate from their reference locations. We provide necessary and sufficient conditions for the candidate to be an equilibrium. We illustrate our results in particular cases including the duopoly competition where we moderate the principle of minimal differentiation.

I want to tell you? Maximizing revenue in first-price two-stage auctionsJournal articleGalit Ashkenazi-Golan, Yevgeny Tsodikovich and Yannick Viossat, Economic Theory, Volume 76, pp. 1329–1362, 2023

A common practice in many auctions is to offer bidders an opportunity to improve their bids, known as a best and final offer stage. This improved bid can depend on new information either about the asset or about the competitors. This paper examines the effects of new information regarding competitors, seeking to determine what information the auctioneer should provide assuming the set of allowable bids is discrete. The rational strategy profile that maximizes the revenue of the auctioneer is the one where each bidder makes the highest possible bid that is lower than his valuation of the item. This strategy profile is an equilibrium for a large enough number of bidders, regardless of the information released. We compare the number of bidders needed for this profile to be an equilibrium under different information structures. We find that it becomes an equilibrium with fewer bidders when less additional information is made available to the bidders regarding the competition. It follows that when the number of bidders is a priori unknown, there are some advantages to the auctioneer not revealing information and conducting a one-stage auction instead.

Increasing Impact of Spain on the Equity Markets of Brazil, Chile and Mexico During the Neoliberal Reforms of the 1990sJournal articleAndrés Rivas, Rahul Verma, Antonio Rodríguez and Pedro H. Albuquerque, Innovation Journal of Social Sciences and Economic Review, Volume 5, Issue 3, pp. 08-20, 2023
Does relationship lending matter in an emerging market?Journal articleNaël Shehadeh, Faicel Belaid, Gilles Dufrénot and Christelle Lecourt, Applied Economics, pp. 1-17, 2023

Based on a unique database (data on 2529 bank-firm relationships of 403 firms from 2012 to 2018) provided by the Central Bank of Tunisia, this article analyses the impact of the intensity and duration of bank-firm relationship on loan quality. By estimating a panel ordered probit model, the results show that the intensity of the lending relationship has a positive (negative) impact on high (medium or low) quality loans. In addition, the duration of the bank-firm relationship increases the probability of low-quality loans. We also find that the impact of relationship lending on loan quality differs according to the level of profitability of the firm. Low and non-performing firms tend to have longer and closer bank relationship, whereas it is the opposite for performing firms. Our results suggest that in an emerging market concentrated around a few banks, longer and closer banking relationships are mainly in favour of low and non-performing firms, reflecting adverse selection and strong moral hazard.

Underreporting of Top Incomes and Inequality: A Comparison of Correction Methods using Simulations and Linked Survey and Tax DataJournal articleEmmanuel Flachaire, Nora Lustig and Andrea Vigorito, Review of Income and Wealth, Volume 69, Issue 4, pp. 1033-1059, 2023

Household surveys do not capture incomes at the top of the distribution well. This yields biased inequality measures. We compare the performance of the reweighting and replacing methods to address top incomes underreporting in surveys using information from tax records. The biggest challenge is that the true threshold above which underreporting occurs is unknown. Relying on simulation, we construct a hypothetical true distribution and a “distorted” distribution that mimics an underreporting pattern found in a novel linked data for Uruguay. Our simulations show that if one chooses a threshold that is not close to the true one, corrected inequality measures may be significantly biased. Interestingly, the bias using the replacing method is less sensitive to the choice of threshold. We approach the threshold selection challenge in practice using the Uruguayan linked data. Our findings are analogous to the simulation exercise. These results, however, should not be considered a general assessment of the two methods.