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**"Comparative statics with linear objectives: normal demand, monotone marginal costs, and ranking multi-prior beliefs"**

**John Quah - John Hopkins University****Mardi 14 juin 2022 - 11 h / 12 h**

Lemma - 4 rue Blaise Desgoffe, 75006 Paris. Salle Maurice Desplas

Abstract:

We formulate a set order on constraint sets which guarantee that linear objective functions on these sets have solutions that vary monotonically in the product order as the constraint set changes with respect to this set order. Using this result, we characterize the utility/production functions that exhibit complementarity/substitutability in factor demand, normality in factor demand, and marginal costs that increase with factor prices. In the context of decision-making under uncertainty, our new set order leads to natural generalizations of first order stochastic dominance in multi-prior models

**“Information Acquisition and Price Discrimination in Dynamic,Decentralized Markets”**

Lemma - 4 rue Blaise Desgoffe, 75006 Paris. Salle Maurice Desplas

Abstract: We formalize a dynamic, decentralized market where consumers with privately-known preferences meet bilaterally with firms. The latter acquire information in order to first-degree price discriminate. Consumers’ endogenous outside options make firms’ information choices strategic complements and can generate multiple equilibria. In some cases, information acquisition prevents convergence to perfect competition when trading frictions vanish. We show the relationship between price discrimination and market power can be negative. For instance, cheaper information intensifies price discrimination, but it can also raise consumer welfare under free entry. At the frictionless limit, consumers can achieve their highest welfare despite some first-degree price discrimination.

**"Deliberation and the Wisdom of Crowds"**

**Franz Dietrich - PSE & CNRS **

**Mardi 31 mai 2022 - 11 h / 12 h**

Lemma - 4 rue Blaise Desgoffe, 75006 Paris. Salle Maurice Desplas

Abstract:

Does pre-voting group deliberation increase majority competence? To address this question, we develop a non-game-theoretic model of opinion formation and deliberation. Two new jury theorems, one pre-deliberation and one post-deliberation, suggest that deliberation is beneficial. Successful deliberation mitigates three voting failures: (1) overcounting widespread evidence, (2) neglecting evidential inequality, and (3) neglecting evidential complementarity. Simulations and theoretic arguments confirm this. But there are five systematic exceptions where deliberation reduces majority competence, always through increasing Failure 1. Our analysis recommends deliberation that is ‘participatory', ‘even', but possibly ‘unequal', i.e., that involves substantive sharing, privileges no evidences, but possibly privileges some persons.

Lemma - 4 rue Blaise Desgoffe, 75006 Paris. Salle Maurice Desplas

Abstract:

We formalize a dynamic, decentralized market where consumers with privately-known preferences meet bilaterally with firms. The latter acquire information in order to first-degree price discriminate. Consumers’ endogenous outside options make firms’ information choices strategic complements and can generate multiple equilibria. In some cases, information acquisition prevents convergence to perfect competition when trading frictions vanish. We show the relationship between price discrimination and market power can be negative. For instance, cheaper information intensifies price discrimination, but it can also raise consumer welfare under free entry. At the frictionless limit, consumers can achieve their highest welfare despite some first-degree price discrimination.

Lemma - 4 rue Blaise Desgoffe, 75006 Paris. Salle Maurice Desplas

Abstract:

We build a theoretical model to explain the complex patterns of income and obesity, accounting for changes in behavior related to exercise. We combine the theory of time allocation with the theory of conspicuous leisure in a growth model, assuming that consumption expenditures connected to exercise time are conspicuous, and that conspicuous behavior changes with economic development. As a result, as economies develop, we show that there is a growing wedge between optimal exercise and consumption choices made by individuals with different income levels. We show that this pattern is connected to a dynamic Kuznets curve linking body weight to economic development over time, and a static Kuznets curve linking different steady state levels of income per worker to body weight. Thus, our model helps explain the rise and slowdown in obesity prevalence in the USA, as well as the positive correlation between obesity and income per worker in developing countries, and the negative correlation between obesity and income per worker in industrialized countries. We supplement our theoretical results with numerical simulations of the static and dynamic obesity Kuznets curves for the USA. We show that while exercise choices have contributed to a slowdown in the rise in obesity prevalence, there is to this date no dynamic Kuznets curve pattern for obesity in the USA. By contrast, we find the existence of a static Kuznets curve: the steady state level of average body weight increases with the per worker stock of capital up to a level of 186.5 pounds, corresponding to a capital stock 25% higher than the current steady state US capital stock, and decreases thereafter. We discuss policy implications of our findings.

Lemma - 4 rue Blaise Desgoffe, 75006 Paris. Salle Maurice Desplas

**Mardi 12 avril 2022 - 11 h / 12 h**

Abstract:

We evaluate the causal effects of a vaccination campaign against Hepatitis B (HB) in France, targeting students in middle and high schools. Using a regression discontinuity approach, we find a strong positive (expected) impact of the campaign on children vaccination rates against HB. Our estimates also reveal a large (unexpected) spillover effect of the campaign: treated individuals are 13 pp. less likely to get their catch-up vaccination against the measles, mumps and rubella, than non treated individuals. As measles is extremely contagious and dangerous, this result, that may be driven by a salience effect on HB, questions the net effect of the campaign.