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National Interests in the European Parliament: Roll Call Vote Analysis

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Transactions on Computational Collective Intelligence XXIII

Part of the book series: Lecture Notes in Computer Science ((TCCI,volume 9760))

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We propose a method for identifying national interests in the European Parliament by comparing roll call vote results with MEPs’ expected ideological positions. We define a new measure – national shift index, corresponding to the magnitude of national delegation’s shift from the aggregate ideological position – which quantifies the influence of the national interest on the voting results. Using this measure, we identify issues characterized by strongest dominance of national factors and compare national delegations’ propensity to vote along national lines.

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  1. 1.

    Felsenthal and Machover identify the three voting choices with −1, 0, and 1, respectively.

  2. 2.

    Under the ordinary rules discussed here there is no voting quorum rule, i.e. the vote is valid irrespective of the number of MEPs present and voting (an absence of the quorum must be raised before the vote is held). In such case, abstentions are effectively equivalent to absence (while in the parliaments with a voting quorum rule they are distinct because they count towards attaining the quorum). However, distinguishing abstentions from absences is still useful, since abstentions always represent an MEP’s decision, while absences can result from circumstances beyond his control (and we cannot distinguish those politically motivated from the random ones). Alternatively, one can use an equivalent model based on the notion of quaternary voting game, where the “not participating” option is considered as the fourth one, see [16].

  3. 3.

    If all members of the k-th political group taking part in the roll call are from the same national delegation, no ideological reference distribution exists for them. In such case, we discard their votes and do not take them into account in further stages of the proposed method. Because those cases are overwhelmingly rare, they do not significantly impact the overall results.

  4. 4.

    It should be noted that this effect may arise when all members have voted according to their respective party lines, but also when some (or even all) members have defected, yet the defections have perfectly balanced each other.

  5. 5.

    This conclusion makes sense from the political analysis point of view: Malta is the country with the stringest anti-abortion laws in the EU, and therefore arguably has an interest in rejecting calls on the EU to intrude (even on a rhetorical layer) on its sovereignty in this area, as such intrusions could in theory end in Malta being forced to change its laws on the subject against the will of its electorate.


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Słomczyński, W., Stolicki, D. (2016). National Interests in the European Parliament: Roll Call Vote Analysis. In: Nguyen, N., Kowalczyk, R., Mercik, J. (eds) Transactions on Computational Collective Intelligence XXIII. Lecture Notes in Computer Science(), vol 9760. Springer, Berlin, Heidelberg.

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