Estimating the Intensive Margin Effect in Panel Data Settings
Javier Viviens
TL;DR
This paper tackles the challenge of estimating the intensive-margin effect of policies in panel data when treatment is not randomly assigned. It embeds a Changes-in-Changes outcome model within Horowitz–Manski–Lee bounds to obtain partial identification of the average and distributional intensive-margin effects for Always-Observed (AO) units, introducing estimands $\text{ATT}_{\text{AO}}$ and $QTT_{AO}(q)$. The author extends the identification to multiple sources of sample selection, relaxing monotonicity under a multi-source framework, and develops consistent, asymptotically normal estimators with confidence intervals for the bounds. An empirical application to a Colombian job-training program demonstrates how the method yields bounds that can include zero—suggesting no intensive-margin effect in that setting—and reveals distributional heterogeneity across outcome quantiles, highlighting the policy-relevance of distributional insights beyond point estimates.
Abstract
Many policies operate through two different channels: the extensive margin (e.g., the decision to participate) and the intensive margin (e.g., the intensity of the response among participants). This paper develops a novel identification strategy to estimate the intensive margin effect in panel data settings. I adapt the Horowitz-Manski-Lee bounds to the Changes-in-Changes framework to partially identify both the average and quantile intensive margin treatment effects. Additionally, I explore how to leverage multiple sources of sample selection to relax the monotonicity assumption in the original Horowitz-Manski-Lee bounds, which may be of independent interest. Alongside the identification strategy, I present estimators and inference results. I illustrate the relevance of the proposed methodology by analyzing a job training program in Colombia.
