Séminaires LEMMA

"Two-way Fixed Effects and Differences-in-Differences Extimators in Hetetogeneous Adoption Designs"

Xavier d'Haultfoeuille

Mardi 21 janvier 2025, 11h-12h

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

Xavier est professeur d’économie au CREST. En 2019, il a obtenu le Prix Malinvaud du meilleur article publié en 2018 par un jeune économiste travaillant en France. Il est managing editor à la Review of Economic Studies. Ses thèmes de recherche sont : théorie économétrique, IO empirique et économie du travail.

Abstract : We consider treatment-effect estimation under a parallel trends assumption, in designs where no unit is treated at period one, all units receive a strictly positive dose at period two, and the dose varies across units. There are therefore no true control groups in such cases. First, we develop a test of the assumption that the treatment effect is mean independent of the treatment, under which the commonly-used two-way-fixed-effects estimator is consistent. When this test is rejected or lacks power, we propose alternative estimators, robust to heterogeneous effects. If there are units with a period-two treatment arbitrarily close to zero, the robust estimator is a difference-in-difference using units with a period-two treatment below a bandwidth as controls. Without such units, we propose non-parametric bounds, and an estimator relying on a parametric specification of treatment-effect heterogeneity. We use our results to revisit Pierce and Schott (2016) and Enikolopov et al. (2011).

"Gender differences in screening on online platform"

Pierre Deschamps, co-écrit avec Guillaume Chapelle, Dylan Glover, Xavier Lambin et Morgane Laouénan.

Mardi 17 décembre 2024, 11h-12h

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

Pierre est Assitant Prof à SOFI (Stockholm University) et a soutenu sa thèse à Sciences Po. Ses thèmes de recherche sont économie du travail, discrimination et économie urbaine

Abstract : There are gender differences in perceptions of safety. Differences in precautionary behavior to avoid unsafe situations can lead to gender gaps in economic outcomes. We show that differences in screening lead to worse economic outcomes for women using a three-pronged approach on a French carpooling platform. First, using a correspondence study with fictitious drivers, we find that female drivers are more likely to be contacted by passengers. Scraped data however, reveals that they are not able to translate this advantage into higher revenues. Using a second correspondence study, we show that female drivers are less likely to reply positively to messages from fictitious passengers, suggesting that they screen passengers more than men do,  reconciling the two previous results.