Research

Working Papers

Point-Identifying Semiparametric Sample Selection Models with No Excluded Variable (with Dongwoo Kim, last revised: February 2025), submitted

arXiv; Cemmap working paper
Abstract: Sample selection is pervasive in applied economic studies. This paper develops semiparametric selection models that achieve identification without relying on exclusion restrictions, an assumption long believed necessary for identification in semiparametric selection models. Our identification conditions require at least one continuously distributed covariate and certain nonlinearity in the selection process. We propose a two-step plug-in estimator that is root-n consistent, asymptotically normal, and computationally straightforward (readily available in statistical software), allowing for heteroskedasticity. Our approach provides a middle ground between Lee (2009)'s nonparametric bounds and Honoré and Hu (2020)'s linear selection bounds, while ensuring point identification. Simulation evidence confirms its excellent finite-sample performance. We apply our method to estimate the racial and gender wage disparity using data from the US Current Population Survey. Our estimates tend to lie outside the Honoré and Hu bounds.

Publications

Semi-Nonparametric Models of Multidimensional Matching: An Optimal Transport Approach (with Dongwoo Kim), Journal of Econometrics, Vol 256, 106242, 2026

Journal article; arXiv; Cemmap working paper

Local Polynomial Estimation of Time-Varying Parameters in Nonlinear Models (with Dennis Kristensen), forthcoming, Econometric Theory

arXiv

Closed-Form Approximations of Moments and Densities of Continuous-Time Markov Models (with Dennis Kristensen and Antonio Mele), Journal of Economic Dynamics and Control, Vol 168, 104948, 2024

Journal article (Open access); arXiv

Vaccination Strategies and Transmission of COVID-19: Evidence across Advanced Countries (with Dongwoo Kim), Journal of Health Economics, Vol 82, 102589, 2022

Journal article (Open access); arXiv; Cemmap working paperMedia: News 1 (Korean); SFU News

Testing for the Presence of Measurement Error in Stata (with Daniel Wilhelm), Stata Journal, Vol 20, Issue 2, 2020

Journal article (Open access); Cemmap working paper; Stata code

Work in Progress

The Impact of EU Enlargement and Brexit on International Migration (with Yoonjung Kim)

Multidimensional Matching and Labor Market Complementarity (with Esben Scriver Andersen)

Sieve Estimation of Optimal Transport with General Surplus

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