Master Thesis: Gelbach in Logit

A Covariate Decomposition for the Logit Model applied to the Minimum Wage’s Heterogeneous Impact

I develop a novel econometric method to decompose the impact that control variables have on the treatment effect in logit models.
Econometrics
Minimum Wage
Statistics
Logit
Author

Miguel Salema

Published

March 13, 2023

Abstract

Sequentially adding control variables to a regression to investigate their effect on a structural parameter is econometrically meaningless when controls are intercorrelated, as the order in which control variables are added will influence how the structural parameters change. As a solution, I develop a novel order-invariant conditional decomposition for the logit model. Furthermore, this logit decomposition can explain which variables are responsible for the heterogeneous treatment effect on the treated. I illustrate the utility of the decomposition with an application. Using a natural experiment to estimate the displacement effects of the minimum wage in Portugal, I find its effects to be heterogeneous. Moreover, by using the decomposition, I find that the heterogeneous impacts are 65% explained by firms, 28% by the worker, and 7% by tenure; implying that the primary determinant of the minimum wage effect on workers’ displacement is the firm they work for.

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Figure I: Omitted Variable Bias in the Logit Model

Figure II: The Effect of the Minimum Wage on the Wage Distribution