A Unified Framework for Spatial and Temporal Treatment Effect Boundaries: Theory and Identification

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Main Author: Kikuchi, Tatsuru
Format: Preprint
Published: 2025
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author Kikuchi, Tatsuru
author_facet Kikuchi, Tatsuru
contents This paper develops a unified theoretical framework for detecting and estimating boundaries in treatment effects across both spatial and temporal dimensions. We formalize the concept of treatment effect boundaries as structural parameters characterizing regime transitions where causal effects cease to operate. Building on reaction-diffusion models of information propagation, we establish conditions under which spatial and temporal boundaries share common dynamics governed by diffusion parameters (delta, lambda), yielding the testable prediction d^*/tau^* = 3.32 lambda sqrt{delta} for standard detection thresholds. We derive formal identification results under staggered treatment adoption and develop a three-stage estimation procedure implementable with standard panel data. Monte Carlo simulations demonstrate excellent finite-sample performance, with boundary estimates achieving RMSE below 10% in realistic configurations. We apply the framework to two empirical settings: EU broadband diffusion (2006-2021) and US wildfire economic impacts (2017-2022). The broadband application reveals a scope limitation -- our framework assumes depreciation dynamics and fails when effects exhibit increasing returns through network externalities. The wildfire application provides strong validation: estimated boundaries satisfy d^* = 198 km and tau^* = 2.7 years, with the empirical ratio (72.5) exactly matching the theoretical prediction 3.32 lambda sqrt{delta} = 72.5. The framework provides practical tools for detecting when localized treatments become systemic and identifying critical thresholds for policy intervention.
format Preprint
id arxiv_https___arxiv_org_abs_2510_00754
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Unified Framework for Spatial and Temporal Treatment Effect Boundaries: Theory and Identification
Kikuchi, Tatsuru
Econometrics
General Economics
Economics
Applications
Methodology
This paper develops a unified theoretical framework for detecting and estimating boundaries in treatment effects across both spatial and temporal dimensions. We formalize the concept of treatment effect boundaries as structural parameters characterizing regime transitions where causal effects cease to operate. Building on reaction-diffusion models of information propagation, we establish conditions under which spatial and temporal boundaries share common dynamics governed by diffusion parameters (delta, lambda), yielding the testable prediction d^*/tau^* = 3.32 lambda sqrt{delta} for standard detection thresholds. We derive formal identification results under staggered treatment adoption and develop a three-stage estimation procedure implementable with standard panel data. Monte Carlo simulations demonstrate excellent finite-sample performance, with boundary estimates achieving RMSE below 10% in realistic configurations. We apply the framework to two empirical settings: EU broadband diffusion (2006-2021) and US wildfire economic impacts (2017-2022). The broadband application reveals a scope limitation -- our framework assumes depreciation dynamics and fails when effects exhibit increasing returns through network externalities. The wildfire application provides strong validation: estimated boundaries satisfy d^* = 198 km and tau^* = 2.7 years, with the empirical ratio (72.5) exactly matching the theoretical prediction 3.32 lambda sqrt{delta} = 72.5. The framework provides practical tools for detecting when localized treatments become systemic and identifying critical thresholds for policy intervention.
title A Unified Framework for Spatial and Temporal Treatment Effect Boundaries: Theory and Identification
topic Econometrics
General Economics
Economics
Applications
Methodology
url https://arxiv.org/abs/2510.00754