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The Triple Difference Estimator

Author

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  • Olden, Andreas

    (Dept. of Business and Management Science, Norwegian School of Economics)

  • Møen, Jarle

    (Dept. of Business and Management Science, Norwegian School of Economics)

Abstract

Triple difference has become a widely used estimator in empirical work. A close reading of articles in top economics journals reveals that the use of the estimator to a large extent rests on intuition. The identifying assumptions are neither formally derived nor generally agreed on. We give a complete presentation of the triple difference estimator, and show that even though the estimator can be computed as the difference between two difference-in-differences estimators, it does not require two parallel trend assumptions to have a causal interpretation. The reason is that the difference between two biased difference-in-differences estimators will be unbiased as long as the bias is the same in both estimators. This requires only one parallel trend assumption to hold.

Suggested Citation

  • Olden, Andreas & Møen, Jarle, 2020. "The Triple Difference Estimator," Discussion Papers 2020/1, Norwegian School of Economics, Department of Business and Management Science.
    • Handle: RePEc:hhs:nhhfms:2020_001
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    File URL: https://hdl.handle.net/11250/2652016
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    More about this item

    Keywords

    Triple difference; difference-in-difference-in-differences; difference-in-differences; DID; DiDiD; parallel trend assumption;
    All these keywords.

    JEL classification:

    • C10 - Mathematical and Quantitative Methods - - Econometric and Statistical Methods and Methodology: General - - - General
    • C18 - Mathematical and Quantitative Methods - - Econometric and Statistical Methods and Methodology: General - - - Methodolical Issues: General
    • C21 - Mathematical and Quantitative Methods - - Single Equation Models; Single Variables - - - Cross-Sectional Models; Spatial Models; Treatment Effect Models

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