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Estimating Treatment Effects in Panel Data Without Parallel Trends

Shoya Ishimaru

arXiv 13 Jan 2026 · Econometrics

arXiv:2601.08281 · PDF · DOI · OpenAlex · Extracted main text

Abstract

This paper proposes a novel approach for estimating treatment effects in panel data settings, addressing key limitations of the standard difference-in-differences (DID) approach. The standard approach relies on the parallel trends assumption, implicitly requiring that unobservable factors correlated with treatment assignment be unidimensional, time-invariant, and affect untreated potential outcomes in an additively separable manner. This paper introduces a more flexible framework that allows for multidimensional unobservables and non-additive separability, and provides sufficient conditions for identifying the average treatment effect on the treated. An empirical application to job displacement reveals substantially smaller long-run earnings losses compared to the standard DID approach, demonstrating the framework's ability to account for unobserved heterogeneity that manifests as differential outcome trajectories between treated and control groups.

Citation extraction

38
references
61
in-text mentions
38
distinct cited
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self-citations
10,871
main-text words

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Most heavily cited references

The works this paper leans on most, across its whole bibliography — not restricted to papers in our corpus. Ranked by composite intensity, which combines how often a work is mentioned, how many sections mention it, and how much of that falls in the main text rather than the appendix.

ReferenceIntensityMentionsSectionsMain text
1Hu and Schennach (2008) Instrumental variable treatment of nonclassical measurement error models1.00093100%
2Sant'Anna and Zhao (2020) Doubly robust difference-in-differences estimators0.7375260%
3Jacobson, LaLonde and Sullivan (1993) Earnings losses of displaced workers0.73732100%
4Freyberger (2018) Non-parametric panel data models with interactive fixed effects0.64441100%
5Athey and Imbens (2006) Identification and inference in nonlinear difference-in-differences models0.64422100%
6Heckman, Ichimura and Todd (1998) Matching as an econometric evaluation estimator0.64422100%
7Jarosch (2023) Searching for job security and the consequences of job loss0.58531100%
8Dauth and Eppelsheimer (2020) Preparing the sample of integrated labour market biographies (SIAB) for scientific analysis: a guide0.5112250%
9Arellano, Blundell and Bonhomme (2017) Earnings and consumption dynamics: a nonlinear panel data framework0.51121100%
10Hu (2017) The econometrics of unobservables: Applications of measurement error models in empirical industrial organization and labor econo…0.40511100%

Showing the top 10 of 38 scored citations.

Cited by, within the corpus

arXiv econ.EM papers that cite this one, ranked by how heavily they lean on it.

Citing paperIntensityMentionsSections
1Event-Study Designs for Discrete Outcomes under Transition Independence0.40511
2MSE-Optimal Difference-in-Differences Estimator0.40511