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When does IV identification not restrict outcomes?

Leonard Goff

arXiv 5 Jun 2024 · Econometrics

arXiv:2406.02835 · PDF · DOI · OpenAlex · Extracted main text

Abstract

Many identification results in instrumental variables (IV) models hold without requiring any restrictions on the distribution of potential outcomes, or how those outcomes are correlated with selection behavior. This enables IV models to allow for arbitrary heterogeneity in treatment effects and the possibility of selection on gains in the outcome. I provide a necessary and sufficient condition for treatment effects to be point identified in a manner that does not restrict outcomes, when the instruments take a finite number of values. The condition generalizes the well-known LATE monotonicity assumption, and unifies a wide variety of other known IV identification results. The result also yields a brute-force approach to reveal all selection models that allow for point identification of treatment effects without restricting outcomes, and then enumerate all of the identified parameters within each such selection model. The search uncovers new selection models that yield identification, provides impossibility results for others, and offers opportunities to relax assumptions on selection used in existing literature. An application considers the identification of complementarities between two cross-randomized treatments, obtaining a necessary and sufficient condition on selection for local average complementarities among compliers to be identified in a manner that does not restrict outcomes. I use this result to revisit two empirical settings, one in which the data are incompatible with this restriction on selection, and another in which the data are compatible with the restriction.

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54
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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
1Blackwell, Matthew (2017) Instrumental Variable Methods for Conditional Effects and Causal Interaction in Voter Mobilization Experiments0.9507386%
2Bai, Yuehao, Huang, Shunzhuang, Moon, Sarah, Shaikh, Azeem M., Vytla… (2024) On the Identifying Power of Monotonicity for Average Treatment Effects0.8435360%
3Navjeevan, Manu, Pinto, Rodrigo, Santos, Andres (2023) Identification and Estimation in a Class of Potential Outcomes Models0.8435360%
4Imbens, Guido W, Angrist, Joshua D (1994) Identification and Estimation of Local Average Treatment Effects0.8229556%
5Angelucci, Manuela, Bennett, Daniel (2024) The Economic Impact of Depression Treatment in India: Evidence from Community-Based Provision of Pharmacotherapy0.78815273%
6(2013) Estimation in an Instrumental Variables Model With Treatment Effect Heterogeneity0.7375340%
7Kirkeboen, Lars J., Leuven, Edwin, Mogstad, Magne (2016) Field of Study, Earnings, and Self-Selection*0.7373367%
8Heckman, James J., Pinto, Rodrigo (2018) Unordered Monotonicity0.6936533%
9Comey, Matthew L., Eng, Amanda R., Pei, Zhuan (2023) Supercompliers0.64422100%
10(2017) Tolerating defiance? Local average treatment effects without monotonicity0.64422100%

Showing the top 10 of 57 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
1On the falsification of instrumental variable models for heterogeneous treatment effects0.73753
2Identification in Multiple Treatment Models under Discrete Variation0.40511
3Potential weights and implicit causal designs in linear regression0.40511
4Inference for Treatment Effects Conditional on Generalized Principal Strata using Instrumental Variables0.40511