Calendrier du 11 janvier 2021
Paris Migration Seminar
Du 11/01/2021 de 17:30 à 18:20
via Zoom
LUKSIC Juan ()
Can immigration affect neighborhood effects? Accounting for the indirect effects of immigrants on native test scores
Migratory waves can affect native students through immigrant peer effects. But immigration and native response can also change neighborhoods. In this paper, I compare two different methods to analyze the impact of immigration on children test scores and show that broader changes in the neighborhood can indeed be important. I study this question by focusing on 4th-grade test scores in the context of the recent migratory phenomenon in Chile, where, from 2012 to 2019, the immigrant population increased from nearly 1% to 8%. Following Chetty and Hendren’s (2018a, 2018b) methodology, I estimate the effect of each municipality on test scores using a fixed effect regression model identified by students who move across municipalities at different ages. Then, I construct a shift-share instrument by taking shares from the 2002 census and estimate the impact of immigrant arrivals on the municipality effects. On average, I find a negative impact of foreign students on the municipality effects. My estimation suggests that a 1 standard deviation increase in the proportion of immigrant students in a municipality causes 1 percentile decrease in student test scores per year spent. Then, I estimate immigrant peer effect (Hoxby, 2000). I find a precise null effect using comparison across school cohorts and classes. These results suggest that migration may affect natives through indirect effects. In fact, the presence of native flights and an increase in socioeconomic segregation across schools fuel the indirect effect hypothesis.
Texte intégral
Paris Game Theory Seminar
Du 11/01/2021 de 11:00 à 12:00
Zoom : https://hec-fr.zoom.us/j/95796468806 ID de réunion : 957 9646 8806
GAUBERT Stéphane (INRIA, CMAP, Ecole Polytechnique)
The geometry of fixed points sets of Shapley operators
écrit avec Marianne Akian and Sara Vannucci
Shapley operators of undiscounted zero-sum two-player games are order-preserving maps that commute with the addition of a constant. The fixed points of these Shapley operators play a key role in the study of games with mean payoff: the existence of a fixed point is guaranteed by ergodicity conditions, moreover, fixed points that are distinct (up to an additive constant) determine distinct optimal stationary strategies. We provide a series of characterizations of fixed point sets of Shapley operators in finite dimension (i.e., for games with a finite state space). Some of these characterizations are of a lattice theoretical nature, whereas some other rely on metric geometry and tropical geometry. More precisely, we show that fixed point sets of Shapley operators are special instances of hyperconvex spaces (non-expansive retracts of sup-norm spaces) that are lattices in the induced partial order. They are also characterized by a property of ``best co-approximation'' arising in the theory of nonexpansive retracts of Banach spaces. Moreover, they retain properties of convex sets, with a notion of ``convex hull'' defined only up to isomorphism. We finally examine the special case of deterministic games with finite action spaces. Then, fixed point sets have a structure of polyhedral complexes, which include as special cases tropical polyhedra. These complexes have a cell decomposition attached to stationary strategies of the players, in which each cell is an alcoved polyhedron of An type.