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Is there a selection bias in roll call votes? Evidence from the European Parliament


  • Simon Hix

    () (London School of Economics and Political Science)

  • Abdul Noury

    () (New York University)

  • Gerard Roland

    () (University of California, Berkeley, CEPR and NBER)


Abstract We examine the magnitude and significance of selection bias in roll call votes. Prior to 2009, all recorded (roll call) votes in the European Parliament had to be requested explicitly by European Political Groups. Since 2009, a roll call vote has been mandatory on all final legislative votes. We exploit that change in the rules and compare differences between final legislative votes, amendment votes and non-legislative votes before and after 2009, using a difference-in-differences approach with extensive controls. Using data from the Sixth (2004–2009) to Seventh (2009–2014) European Parliaments, we fail to find any large differences in voting cohesion for the main political groups. We find even less significance when we control for changes in parliamentary membership between those two periods. The results suggest that selection biases in the European Parliament associated with strategic choices are negligible.

Suggested Citation

  • Simon Hix & Abdul Noury & Gerard Roland, 2018. "Is there a selection bias in roll call votes? Evidence from the European Parliament," Public Choice, Springer, vol. 176(1), pages 211-228, July.
  • Handle: RePEc:kap:pubcho:v:176:y:2018:i:1:d:10.1007_s11127-018-0529-1
    DOI: 10.1007/s11127-018-0529-1

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    References listed on IDEAS

    1. Hix, Simon & Noury, Abdul, 2016. "Government-Opposition or Left-Right? The Institutional Determinants of Voting in Legislatures," Political Science Research and Methods, Cambridge University Press, vol. 4(02), pages 249-273, May.
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    10. Hix, Simon & Noury, Abdul & Roland, G Rard, 2005. "Power to the Parties: Cohesion and Competition in the European Parliament, 1979 2001," British Journal of Political Science, Cambridge University Press, vol. 35(02), pages 209-234, April.
    11. Abdul Ghafar Noury & Simon Hix & Gérard Roland, 2007. "Democratic politics in the European Parliament," ULB Institutional Repository 2013/7744, ULB -- Universite Libre de Bruxelles.
    12. Abdul G. Noury & Gérard Roland, 2002. "More power to the European Parliament?," Economic Policy, CEPR;CES;MSH, vol. 17(35), pages 279-319, October.
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    More about this item


    Roll call votes; European Parliament; Party discipline; Natural experiment; Difference in difference estimation;

    JEL classification:

    • P16 - Economic Systems - - Capitalist Systems - - - Political Economy of Capitalism
    • P48 - Economic Systems - - Other Economic Systems - - - Political Economy; Legal Institutions; Property Rights; Natural Resources; Energy; Environment; Regional Studies
    • D72 - Microeconomics - - Analysis of Collective Decision-Making - - - Political Processes: Rent-seeking, Lobbying, Elections, Legislatures, and Voting Behavior
    • D78 - Microeconomics - - Analysis of Collective Decision-Making - - - Positive Analysis of Policy Formulation and Implementation


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