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Heterogeneous Policy Effects in Comparative Case Studies with Treated-Unit Microdata

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  • Carl Bonander

Abstract

This article develops an identification framework for heterogeneous policy effects when individual-level data are available only in the treated jurisdiction. The framework combines outcome changes from repeated cross-sections within that jurisdiction with a population-average effect identified from aggregate panel data. Under conditional relative parallel trends and overlap, this information identifies subgroup effects standardized to the treated jurisdiction's overall post-treatment covariate distribution, but generally not effects averaged over each subgroup's own distribution. I establish how these subgroup-average effects can nevertheless be recovered using covariate-specific aggregate effects or additional pretreatment observations under assumptions about the evolution of untreated trends. Simulations and an application to the Massachusetts health reform illustrate the framework.

Suggested Citation

  • Carl Bonander, 2026. "Heterogeneous Policy Effects in Comparative Case Studies with Treated-Unit Microdata," Papers 2609.28678, arXiv.org, revised Oct 2026.
    • Handle: RePEc:arx:papers:2609.28678
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    References listed on IDEAS

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