IDEAS home Printed from https://ideas.repec.org/a/taf/apeclt/v26y2019i5p358-361.html
   My bibliography  Save this article

Alternatives to polynomial trend-corrected differences-in-differences models

Author

Listed:
  • Vincent Vandenberghe

Abstract

A common problem with differences-in-differences (DD) estimates is the failure of the parallel-trend assumption. To cope with this, most authors include polynomial (linear, quadratic…) trends among the regressors, and estimate the treatment effect as a once-in-a-time trend shift. In practice, that strategy does not work very well, because inter alia the estimation of the trend uses post-treatment data. An extreme case is when sample covers only one period before treatment and many after. Then the trend’s estimate relies almost completely on post-treatment developments, and absorbs most of the treatment effect. What is needed is a method that i) uses pretreatment observations to capture linear or nonlinear trend differences, and ii) extrapolates these to compute the treatment effect. This article shows how this can be achieved using a fully flexible version of the canonical DD equation. It also contains an illustration using data on a 1994–2000 EU programme that was implemented in the Belgian province of Hainaut.

Suggested Citation

  • Vincent Vandenberghe, 2019. "Alternatives to polynomial trend-corrected differences-in-differences models," Applied Economics Letters, Taylor & Francis Journals, vol. 26(5), pages 358-361, March.
    • Handle: RePEc:taf:apeclt:v:26:y:2019:i:5:p:358-361
    DOI: 10.1080/13504851.2018.1478386
    as

    Download full text from publisher

    File URL: http://hdl.handle.net/10.1080/13504851.2018.1478386
    Download Restriction: Access to full text is restricted to subscribers.
    File URL: https://libkey.io/10.1080/13504851.2018.1478386?utm_source=ideas
    LibKey link: if access is restricted and if your library uses this service, LibKey will redirect you to where you can use your library subscription to access this item
    ---><---

    As the access to this document is restricted, you may want to look for a different version below or search for a different version of it.

    Other versions of this item:

    References listed on IDEAS

    as
    1. Joshua D. Angrist & Jörn-Steffen Pischke, 2009. "Mostly Harmless Econometrics: An Empiricist's Companion," Economics Books, Princeton University Press, edition 1, number 8769.
    2. David H. Autor, 2003. "Outsourcing at Will: The Contribution of Unjust Dismissal Doctrine to the Growth of Employment Outsourcing," Journal of Labor Economics, University of Chicago Press, vol. 21(1), pages 1-42, January.
    3. Leora Friedberg, 1998. "Did Unilateral Divorce Raise Divorce Rates? Evidence from Panel Data," NBER Working Papers 6398, National Bureau of Economic Research, Inc.
    4. Timothy Besley & Robin Burgess, 2004. "Can Labor Regulation Hinder Economic Performance? Evidence from India," The Quarterly Journal of Economics, President and Fellows of Harvard College, vol. 119(1), pages 91-134.
    5. Vincent Vandenberghe, 2016. "Treatment-Effect Identification Without Parallel paths An illustration in the case of Objective 1- Hainaut/Belgium, 1994-2006," Working Papers CEB 16-051, ULB -- Universite Libre de Bruxelles.
    6. Justin Wolfers, 2006. "Did Unilateral Divorce Laws Raise Divorce Rates? A Reconciliation and New Results," American Economic Review, American Economic Association, vol. 96(5), pages 1802-1820, December.
    7. Mora, Ricardo & Reggio, Iliana, 2012. "Treatment effect identification using alternative parallel assumptions," UC3M Working papers. Economics we1233, Universidad Carlos III de Madrid. Departamento de Economía.
    Full references (including those not matched with items on IDEAS)

    Citations

    Citations are extracted by the CitEc Project, subscribe to its RSS feed for this item.
    as


    Cited by:

    1. Vandenberghe, Vincent, 2018. "Treatment-effect identification without parallel paths," Economics - The Open-Access, Open-Assessment E-Journal (2007-2020), Kiel Institute for the World Economy (IfW Kiel), vol. 12, pages 1-19.
    2. Jo, Wooyong & Nam, Hyoryung & Choi, Jeonghye, 2022. "Opening the OTC drug market: The effect of deregulation on retail pharmacy’s performance," International Journal of Research in Marketing, Elsevier, vol. 39(3), pages 847-866.
    3. Annarita Macchioni Giaquinto, 2022. "The power of the (red) pill in Europe: pharmaceutical innovation and female empowerment," Working Papers 2022:09, Department of Economics, University of Venice "Ca' Foscari".

    Most related items

    These are the items that most often cite the same works as this one and are cited by the same works as this one.
    1. Daniela Vuri, 2018. "Joint custody law and mothers’ labor market outcomes: evidence from the USA," Journal of Population Economics, Springer;European Society for Population Economics, vol. 31(4), pages 1203-1237, October.
    2. Savelkoul, Ruben, 2020. "Superstars vs the long tail: How does music piracy affect digital song sales for different segments of the industry?," Information Economics and Policy, Elsevier, vol. 50(C).
    3. Gallego, Jorge & Maldonado, Stanislao & Trujillo, Lorena, 2020. "From curse to blessing? institutional reform and resource booms in Colombia," Journal of Economic Behavior & Organization, Elsevier, vol. 178(C), pages 174-193.
    4. Dang, Viet A. & De Cesari, Amedeo & Phan, Hieu V., 2021. "Employment protection and share repurchases: Evidence from wrongful discharge laws," Journal of Corporate Finance, Elsevier, vol. 69(C).
    5. Johanna Catherine Maclean & Michael F. Pesko & Steven C. Hill, 2017. "The Effect of Insurance Expansions on Smoking Cessation Medication Prescriptions: Evidence from ACA Medicaid Expansions," NBER Working Papers 23450, National Bureau of Economic Research, Inc.
    6. Gary Solon & Steven J. Haider & Jeffrey M. Wooldridge, 2015. "What Are We Weighting For?," Journal of Human Resources, University of Wisconsin Press, vol. 50(2), pages 301-316.
    7. Popovici, Ioana & Maclean, J. Catherine & French, Michael, 2017. "The Effects of Health Insurance Parity Laws for Substance Use Disorder Treatment on Traffic Fatalities: Evidence of Unintended Benefits," IZA Discussion Papers 10746, Institute of Labor Economics (IZA).
    8. Brutti Zelda, 2020. "Cities drifting apart: Heterogeneous outcomes of decentralizing public education," IZA Journal of Labor Economics, Sciendo & Forschungsinstitut zur Zukunft der Arbeit GmbH (IZA), vol. 9(1), pages 1-38, January.
    9. Johanna Catherine Maclean & Benjamin L. Cook & Nicholas Carson & Michael F. Pesko, 2017. "Public Insurance and Psychotropic Prescription Medications for Mental Illness," NBER Working Papers 23760, National Bureau of Economic Research, Inc.
    10. Lee Jin Young & Solon Gary, 2011. "The Fragility of Estimated Effects of Unilateral Divorce Laws on Divorce Rates," The B.E. Journal of Economic Analysis & Policy, De Gruyter, vol. 11(1), pages 1-11, August.
    11. Sergio Destefanis & Matteo Fragetta & Emanuel Gasteiger, 2024. "Does one size fit all in the Euro Area? Some counterfactual evidence," Empirical Economics, Springer, vol. 67(4), pages 1615-1647, October.
    12. Ioana Popovici & Johanna Catherine Maclean & Michael T. French, 2017. "Health Insurance and Traffic Fatalities: The Effects of Substance Use Disorder Parity Laws," NBER Working Papers 23388, National Bureau of Economic Research, Inc.
    13. Papini, Andrea, 2018. "Tax incentives and the choice of organisational form of small businesses. Identification through a differentiated payroll tax schedule," ISER Working Paper Series 2018-07, Institute for Social and Economic Research.
    14. Paul Demeré, 2023. "Is tax return information useful to equity investors?," Review of Accounting Studies, Springer, vol. 28(3), pages 1413-1465, September.
    15. Maclean Johanna Catherine & Cook Benjamin & Carson Nicholas & Pesko Michael F, 2019. "Public Health Insurance and Prescription Medications for Mental Illness," The B.E. Journal of Economic Analysis & Policy, De Gruyter, vol. 19(1), pages 1-25, January.
    16. Katie R. Genadek & Wendy A. Stock & Christiana Stoddard, 2007. "No-Fault Divorce Laws and the Labor Supply of Women with and without Children," Journal of Human Resources, University of Wisconsin Press, vol. 42(1).
    17. DAVID M. BLAU & WILBERT van der KLAAUW, 2013. "What Determines Family Structure?," Economic Inquiry, Western Economic Association International, vol. 51(1), pages 579-604, January.
    18. Gordon Dahl, 2010. "Early teen marriage and future poverty," Demography, Springer;Population Association of America (PAA), vol. 47(3), pages 689-718, August.
    19. Uribe-Castro, Mateo, 2019. "Expropriation of church wealth and political conflict in 19th century Colombia," Explorations in Economic History, Elsevier, vol. 73(C), pages 1-1.
    20. Cain Polidano & Justin van de Ven & Sarah Voitchovsky, 2017. "The Power of Self-Interest: Effects of Education and Training Entitlements in Later-Life," Melbourne Institute Working Paper Series wp2017n12, Melbourne Institute of Applied Economic and Social Research, The University of Melbourne.

    More about this item

    JEL classification:

    • C21 - Mathematical and Quantitative Methods - - Single Equation Models; Single Variables - - - Cross-Sectional Models; Spatial Models; Treatment Effect Models
    • C4 - Mathematical and Quantitative Methods - - Econometric and Statistical Methods: Special Topics
    • C5 - Mathematical and Quantitative Methods - - Econometric Modeling

    Statistics

    Access and download statistics

    Corrections

    All material on this site has been provided by the respective publishers and authors. You can help correct errors and omissions. When requesting a correction, please mention this item's handle: RePEc:taf:apeclt:v:26:y:2019:i:5:p:358-361. See general information about how to correct material in RePEc.

    If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.

    If CitEc recognized a bibliographic reference but did not link an item in RePEc to it, you can help with this form .

    If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your RePEc Author Service profile, as there may be some citations waiting for confirmation.

    For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: Chris Longhurst (email available below). General contact details of provider: http://www.tandfonline.com/RAEL20 .

    Please note that corrections may take a couple of weeks to filter through the various RePEc services.

    IDEAS is a RePEc service. RePEc uses bibliographic data supplied by the respective publishers.