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Weights to address non‐parallel trends in panel difference‐in‐differences models

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  • Ahlfeldt, Gabriel M.

Abstract

Causal inference using the difference‐in‐differences (DD) method relies on the untestable assumption of parallel counterfactual trends across units that are assigned to different treatments. To facilitate the application of the method in settings where the parallel‐trends assumption is seemingly violated, I suggest weighting observations such that the conditional correlations between treatments and pre‐treatment outcome trends are minimised, i.e. weighted trends are parallel. I evaluate the performance of a weighted parallel trends (WPT) DD estimator in a Monte Carlo study and provide an application to a case‐study context in which a benchmark estimate exists. The WPT DD approach can be applied in settings with multiple continuous treatment variables as well as to estimating time‐varying treatment effects.

Suggested Citation

  • Ahlfeldt, Gabriel M., 2018. "Weights to address non‐parallel trends in panel difference‐in‐differences models," LSE Research Online Documents on Economics 87666, London School of Economics and Political Science, LSE Library.
    • Handle: RePEc:ehl:lserod:87666
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    Cited by:

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    2. Ahlfeldt, Gabriel M. & Nitsch, Volker & Wendland, Nicolai, 2019. "Ease versus noise: long-run changes in the value of transport (dis)amenities," LSE Research Online Documents on Economics 102824, London School of Economics and Political Science, LSE Library.
    3. Pan, Yan & Zhong, Wen-fang & Yin, Rong & Zheng, Meng & Xie, Kun & Cheng, Shu-yuan & Ling, Li & Chen, Wen, 2022. "Does direct settlement of intra-province medical reimbursements improve financial protection among middle-aged and elderly population in China? Evidence based on CHARLS data," Social Science & Medicine, Elsevier, vol. 308(C).
    4. Difan Liu & Yuejian Wang & Yuejiao Chen & Guang Yang & Hailiang Xu & Yuxiang Ma, 2022. "Analysis of the Difference in Changes to Farmers’ Livelihood Capital under Different Land Transfer Modes—A Case Study of Manas County, Xinjiang, China," Land, MDPI, vol. 11(8), pages 1-19, August.
    5. Panzone, Luca A., 2022. "Conditional Promotion With A Costly Reward: An Evaluation Of A Campaign To Motivate Consumption Of Fruit And Vegetables," 2022 Annual Meeting, July 31-August 2, Anaheim, California 322058, Agricultural and Applied Economics Association.
    6. Renan Almeida & Marcelo Brandão & Ramon Torres & Pedro Patrício & Pedro Amaral, 2021. "An assessment of the impacts of large‐scale urban projects on land values: The case of Belo Horizonte, Brazil," Papers in Regional Science, Wiley Blackwell, vol. 100(2), pages 517-559, April.

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    More about this item

    Keywords

    Access; difference‐in‐differences; land price; matching; Monte Carlo; noise; weights; AZ.10.10.2.070;
    All these keywords.

    JEL classification:

    • N73 - Economic History - - Economic History: Transport, International and Domestic Trade, Energy, and Other Services - - - Europe: Pre-1913
    • N74 - Economic History - - Economic History: Transport, International and Domestic Trade, Energy, and Other Services - - - Europe: 1913-
    • R12 - Urban, Rural, Regional, Real Estate, and Transportation Economics - - General Regional Economics - - - Size and Spatial Distributions of Regional Economic Activity; Interregional Trade (economic geography)
    • R14 - Urban, Rural, Regional, Real Estate, and Transportation Economics - - General Regional Economics - - - Land Use Patterns
    • R41 - Urban, Rural, Regional, Real Estate, and Transportation Economics - - Transportation Economics - - - Transportation: Demand, Supply, and Congestion; Travel Time; Safety and Accidents; Transportation Noise

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