Tying the politicians’ hands: The optimal limits to representative democracyJournal articleDidier Laussel et Ngo Van Long, Journal of Public Economic Theory, Volume 22, Issue 1, pp. 25-48, 2020

The citizen candidate models of democracy assume that politicians have their own preferences that are not fully revealed at the time of elections. We study the optimal delegation problem which arises between the median voter (the writer of the constitution) and the (future) incumbent politician under the assumption that not only the state of the world but also the politician's type (preferred policy) are the policy-maker's private information. We show that it is optimal to tie the hands of the politician by imposing both a policy floor and a policy cap and delegating him/her the policy choice only in between the cap and the floor. The delegation interval is shown to be the smaller the greater is the uncertainty about the politician's type. These results are also applicable to settings outside the specific problem that our model addresses.

Marketplace or reselling? A signalling modelJournal articleNada Belhadj, Didier Laussel et Joana Resende, Information Economics and Policy, Volume 50, pp. 100834, 2020

This paper shows that the platforms’ private information on demand may explain the empirical observation that platforms like Amazon resell high-demand products, while acting as marketplace for low-demand goods. More precisely, the paper examines the strategic interaction between a seller and a better informed platform within a signalling game. We consider that the platform may choose between two distinct business models: act as a reseller or work as a pure marketplace between the buyers and the seller. The marketplace mode, which allows to internalize the spillover between the platform’s sales and the seller’s direct sales is always preferred for a low-value good. The reselling mode, which allows the platform to take advantage of its private information, may be selected in the case of high-value goods provided that (i) the externalities between direct sales and platform sales are not too strong and (ii) the difference between consumers’ willingness to pay for the high and the low-value goods is large enough. Under these conditions, the game displays a Least-Cost Separating Equilibrium in which the platform works as a marketplace for low-demand goods, while it acts as a reseller in the case of high-demand goods.

Quality and price personalization under customer recognition: A dynamic monopoly model with contrasting equilibriaJournal articleDidier Laussel, Ngo Van Long et Joana Resende, Journal of Economic Dynamics & Control, Volume 114, pp. 103869, 2020

We present a model of market hyper-segmentation, where a monopolist acquires within a short time all information about the preferences of consumers who purchase its vertically differentiated products. The firm offers a new price/quality schedule after each commitment period. Lower consumer types may have an incentive to delay their purchases until next period to obtain a better introductory offer. The monopolist counters this incentive by offering higher informational rents. Considering the dynamic game played by the monopolist and its customers, we find that there is always a Markov perfect equilibrium (MPE) in which the firm immediately sells the good to all customers, offering the Mussa-Rosen static equilibrium schedule to first time customers (and getting full commitment profits). However, if the commitment period between two offers is long enough, there is another MPE with gradual market expansion. Contrary to the Coasian result for a durable-good monopoly, we find that in both equilibria the profit of the monopolist increases (and the aggregate consumers surplus decreases) as the interval of commitment shrinks. The model yields policy implications for regulations on collection and storage of customers information. (C) 2020 Elsevier B.V. All rights reserved.

The curse of knowledge: having access to customer information can reduce monopoly profitsJournal articleDidier Laussel, Ngo Long et Joana Resende, Rand Journal of Economics, Volume 51, Issue 3, pp. 650-675, 2020

We show that a monopolist's profit is higher if he refrains from collecting coarse information on his customers, sticking to constant uniform pricing rather than recognizing customers' segments through their purchase history. In the Markov perfect equilibrium with coarse information collection, after each commitment period, a new introductory price is offered to attract new customers, creating a new market segment for price discrimination. Eventually, the whole market is covered. Shortening the commitment period results in lower profits. These results sharply differ from the ones obtained when the firm can uncover the exact willingness-to-pay of each previous customer.

Complementary Monopolies with asymmetric informationJournal articleDidier Laussel et Joana Resende, Economic Theory, Volume 70, Issue 4, pp. 943-981, 2020

We investigate how asymmetric information on final demand affects strategic interaction between a downstream monopolist and a set of upstream monopolists, who independently produce complementary inputs. We study an intrinsic private common agency game in which each supplieriindependently proposes a pricing schedule contract to the assembler, specifying the supplier's payment as a function of the assembler's purchase of inputi. We provide a necessary and sufficient equilibrium condition. A lot of equilibria satisfy this condition but there is a unique Pareto-undominated Nash equilibrium from the suppliers' point of view. In this equilibrium, there are unavoidable efficiency losses due to excessively low sales of the good. However, suppliers may be able to limit these distortions by implicitly coordinating on an equilibrium with a rigid (positive) output in bad demand circumstances.

The determination of public tuition fees in a mixed education system: A majority voting modelJournal articleHejer Lasram et Didier Laussel, Journal of Public Economic Theory, Volume 21, Issue 6, pp. 1056-1073, 2019

We study the determination of public tuition fees through majority voting in a vertical differentiation model where agents' returns on educational investment differ and public and private universities coexist and compete in tuition fees. The private university offers higher educational quality than its competitor, incurring higher unit cost per trained student. The tuition fee for the state university is fixed by majority voting while that for the private follows from profit maximization. Then agents choose to train at the public university or the private one or to remain uneducated. The tax per head adjusts in order to balance the state budget. Because there is a private alternative, preferences for education are not single-peaked and no single-crossing condition holds. An equilibrium is shown to exist, which is one of three types: high tuition fee (the “ends” are a majority), low tuition fee (the “middle” is a majority), or mixed (votes tie). The cost structure determines which equilibrium obtains. The equilibrium tuition is either greater (majority at the ends) or smaller (majority at the middle) than the optimal one.

Strategic Product Design under DuopolyJournal articleDidier Laussel, Annals of Economics and Statistics, Issue 131, pp. 25-44, 2018

Two duopolists first decide in which proportions to incorporate in their product two different Lancasterian characteristics and then compete in quantities or prices. In the Cournot case, minimum differentiation obtains at equilibrium whatever the degree of substituability between the characteristics. In the Bertrand one, the equilibrium depends crucially on the degree of substituability/complementarity between the two characteristics. Maximal differential obtains if and only if the characteristics are strong enough substitutes. On the contrary as characteristics become closer and closer complements one obtains in the limit a minimal differentiation result. JEL Codes: L13. Keyword: Horizontal Product Differentiation, Lancasterian Characteristics.

When do imperfectly competitive firms maximize profits? The lessons from a simple general equilibrium model with shareholders’ votingJournal articleRim Lahmandi-Ayed et Didier Laussel, Journal of Mathematical Economics, Volume 78, Issue C, pp. 6-12, 2018

We consider a general equilibrium model with vertical preferences, where workers and consumers are differentiated, respectively, by their sensitivity to effort and their intensity of preference for quality. We consider a monopoly of which the shares are owned by a fraction of the general population. The price is determined through a vote among all the shareholders. We identify necessary and sufficient conditions for (i) an absolute (relative) majority to vote for the profit maximizing price; (ii) an absolute (relative) majority to vote for a different price. We argue that the more concentrated the ownership the more likely it is that the firm charges the profit-maximizing price.

Simple centrifugal incentives in spatial competitionJournal articleDimitrios Xefteris, Didier Laussel et Michel Le Breton, International Journal of Game Theory, Volume 46, Issue 2, pp. 357-381, 2017

This paper studies the effects of introducing centrifugal incentives in an otherwise standard Downsian model of electoral competition. First, we demonstrate that a symmetric equilibrium is guaranteed to exist when centrifugal incentives are induced by any kind of partial voter participation (such as abstention due to indifference, abstention due to alienation, etc.) and, then, we argue that: (a) this symmetric equilibrium is in pure strategies, and it is hence convergent, only when centrifugal incentives are sufficiently weak on both sides; (b) when centrifugal incentives are strong on both sides (when, for example, a lot of voters abstain when they are sufficiently indifferent between the two candidates) players use mixed strategies—the stronger the centrifugal incentives, the larger the probability weight that players assign to locations near the extremes; and (c) when centrifugal incentives are strong on one side only—say for example only on the right—the support of players’ mixed strategies contain all policies except from those that are sufficiently close to the left extreme.

Democracy and competition: Vertical differentiation and labor in a general equilibrium modelJournal articleAmani Kahloul, Rim Lahmandi-Ayed, Hejer Lasram et Didier Laussel, Journal of Public Economic Theory, Volume 19, Issue 4, pp. 860-874, 2017

We consider a general equilibrium model with vertical preferences and one or two firms, where workers and consumers are differentiated, respectively, by their sensitivity to effort and their preference for quality. The question in this paper is whether a decentralized choice through majority vote would lead to more or less competition. We compare the duopoly and the monopoly cases from the viewpoint of each individual, then we deduce the choice of the majority. We prove that, under concentrated ownership (where owners have a null density), duopoly is always preferred by the majority; while under egalitarian ownership (where firms are equally shared by all the population), the choice of the majority depends on the relative size of workers' and consumers' segments.