Research

Working Papers

1. Pitfalls of Common Estimators for Continuous Dynamic Treatments

with Jan Stuhler

Abstract  ·  Version: May 2026

We examine commonly used estimators for continuous treatments that vary over time. The classical static panel regression that relates outcomes to current treatment intensity does not accurately capture lagged effects. The most commonly used dynamic difference-in-differences regression instead uses a time-constant measure of treatment to estimate period-specific coefficients, capturing dynamic effects more accurately. We show, however, when higher-exposed units accumulate their treatment earlier than less-exposed units -- a pattern we document for immigration and labor demand shocks -- the estimated coefficients become harder to interpret causally. A panel regression including leads and lags of the time-varying treatment provides an alternative that is robust to these concerns, although it requires sufficient time-series variation in the treatment. We characterize when each estimator fails to recover the treatment effects, propose diagnostic tests, and discuss additional complications arising from heterogeneous treatment effects.

2. Retail Expansion in Developing Countries: Evidence from Hard Discount Stores

with Andrés Calderón & Andrea Otero-Cortés

R&R · Journal of Development Economics

WP: Banco de la República

Abstract  ·  Version: April 2026

The expansion of modern retail in developing countries has reshaped an industry historically dominated by traditional, informal retailers. Its consequences for labor markets, however, remain poorly understood. We study the staggered entry of hard discount stores into small Colombian municipalities between 2010 and 2019. Combining social security records with household survey and tax data, we find that following the entry of a discount chain, the formal employment-to-population ratio increases by approximately 10 percent over time. Formality rises in commerce, manufacturing, and construction, along with tax revenues in those sectors. We also find no significant effects on informal employment. Our results suggest that modern retail expansion in highly informal contexts can foster labor formalization.

3. Wage-Setting Constraints and Firm Responses to Demand Shocks

with Manudeep Bhuller, Santiago Hermo & Linnea Lorentzen

🏆 Best Paper · CUFE Forum 2025
Abstract  ·  Version: May 2026

This paper investigates how institutional wage-setting constraints, such as a national minimum wage or collectively bargained wages, affect firm responses to demand shocks. We develop a framework to interpret heterogeneous shock responses that depend on the constraints firms face, and provide empirical evidence on the relevance of these constraints in shaping firm behavior across three countries with different institutional settings: Portugal, Norway, and Colombia. We discuss the implications of our findings for conventional estimates of rent-sharing and employer wage-setting power.

4. Worker Responses to Immigration Across Firms: Evidence from Colombia
🏆 Best Immigration Paper · OECD Conference 2023

WP: RFBerlin

Coverage: uc3nomics blog · PSE Migration policy briefs

Abstract  ·  Version: April 2026

The labor market effects of immigration depend on how firms adjust, yet this aspect remains unexplored in developing countries. This paper studies the mass influx of Venezuelan migrants into Colombia using employer-employee data. As immigrants enter informal employment, formal employment for minimum-wage natives declines, reflecting their substitutability with lower-cost informal workers. The negative effects are stronger in small formal firms, which rely more on informality. A machine learning analysis shows that firm-level factors explain more of the heterogeneity in worker-level impacts. These findings highlight that informality amplifies the role of firms in shaping workers' adjustments to immigration.

5. Monopsony Power and Firm Organization

with Álvaro Jáñez

WP: RFBerlin

Abstract  ·  Version: October 2025

Labor market competition differs drastically for production workers and managers. We extend a general equilibrium oligopsony model with minimum wages to include firm organization: firms trade off hiring managers to expand their number of production workers against higher costs. Using matched employer-employee and balance sheet data of Portuguese firms, we quantify the model and validate it against quasi-experimental evidence on oligopsony and minimum wage effects. Relative to the efficient economy, monopsony power reduces employment, wages, and employment concentration, particularly for managers. Hence, welfare losses are 3.4 and 2.4 percent for managers and production workers, respectively. Managers bear greater losses because they sort into larger firms, view firms' non-wage attributes as less substitutable, and are less likely to be bound by the minimum wage. Moreover, monopsony over managers alone reduces production workers' earnings by one-fifth through production complementarities.

6. Firms, Regularization, and Immigrant Integration
Abstract  ·  Version: April 2026

This paper examines the labor market integration of millions of migrants in Colombia during a large-scale regularization program. Using labor force survey data on Venezuelan-born migrants in the informal sector and longitudinal data for the universe of regularized migrants in the formal sector, I uncover substantial disparities. The most pronounced gap is in formality: migrants are about 70% more likely to work informally than comparable natives. Despite the regularization program, only 10% of regularized migrants had formal jobs by 2021. Among those entering the formal sector, they typically work in minimum-wage jobs and in small, low-paying firms, earning around two-thirds as much as comparable natives. I find that close to 50% of the overall wage gap between them is due to migrant sorting into firms with lower pay policies. While there are improvements as migrants gain formal sector experience, a persistent gap remains. I discuss, using some evidence and theory, why formalization rates remain low despite migrants' similar language, culture, education, and access to work permits.


Publications

1. Immigration, Wages, and Employment under Informal Labor Markets
Journal of Population Economics · 2024 · Vol 37, Art 55  

WP: UC3M SocArXiv RieC

Abstract

This paper studies the labor market impacts of the Venezuelan immigration in Colombia. Exploiting spatial variation in exposure, I find a negative effect on native wages driven by the informal sector (where immigrants are concentrated) and a reduction in native employment in the formal sector (where the minimum wage binds for many workers). To explain this, I build a model in which a firm substitutes formal for informal labor in response to lower informal wages. Consistent with the model's predictions, I document that the decrease in formal employment is driven by small firms that use both labor types in production and by workers earning the minimum wage.


Work in Progress


Policy Reports