The authors contribute to the existing literature on the determinants of legislative voting by offering a social network-based theory about the ways that legislators’ social relationships affect floor voting behaviour. It is argued that legislators establish contacts with both political friends and enemies, and that they use the information they receive from these contacts to increase their confidence in their own policy positions. Social contacts between political allies have greater value the more the two allies agree on policy issues, while social contacts between political adversaries have greater value the more the two adversaries disagree on policy issues. To test these propositions, we use social network analysis tools and demonstrate how to account for network dependence using a multilevel modelling approach.
Department of Political Science, University of Wisconsin, Madison (email:
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35 Note that a case in which a legislator seeks information from a source whose position is unknown is observationally equivalent to a situation in which the source of information is objective or neutral. This is because in both cases Legislator A can have no expectation of what her source's position ought to be and how it relates to her own predisposition. It is worth emphasizing, however, that a truly objective source should be a rare occurrence in the context of our discussion (if it exists at all) since our main focus is on contacts between legislators. We do not conceive of legislators as political actors who can be truly objective or neutral, because they seek to achieve distinct political objectives and they have a stake in the public policy they make. Moreover, even if a source were objectively neutral, the recipient of the information cannot be certain that she is, in fact, provided with unprejudiced information. As a result, the major categories that are meaningful in our theoretical context are legislators whose positions are either predictable or uncertain.
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54 Survey questions can be found in Appendix A. The survey was hosted by Surveymonkey.com.
55 English and French are the working languages of the EU. The great majority of legislative assistants, if not all, speak at least one of these languages. We also made the questionnaire available in German because more MEPs are native German speakers than any other language.
56 In fact, we tried collecting equivalent data in the US Congress and found not a single person who was willing to divulge this information.
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60 We received one staffer response per office after sending a general request for a survey response to each MEP office. The sample of interview respondents shows that the staffers responsible for environmental issues were the ones who responded to our questionnaire, which gives us confidence that the network we identify is truly the EP ‘environmental policy’ network.
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64 Three members, from Bulgaria and Romania, were excluded because they joined the EP in January 2007.
65 Interviews were conducted in June and July 2007.
66 This is ‘unbalanced’ in the sense that we will have had two opportunities to observe contacts for dyads consisting of two survey respondents, but only one chance to observe dyads with one respondent and one non-respondent. We suspect that the most careful way to handle this discrepancy would be to think of social contact as the latent variable of interest, which is then measured with error that depends on the opportunities to observe contact. We plan to explore this in a subsequent technical paper.
67 The dependent variable, percentage of votes in common, is of course itself an undirected relation.
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69 We are withholding further information about the party affiliation of these members, because to do otherwise would allow readers to identify the MEPs and we wish to protect the anonymity of our study participants.
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72 At the request of anonymous reviewers, we calculated alternative connectivity measures, such as maximum flow; however, we found our results to be sensitive to such specification changes. We are not altogether surprised about the sensitivity of the results, because we have a small sample size and have collected specialized and unique data. The only way to rectify this problem and increase the robustness of the findings is to collect further survey data on connectivity, which is of course impossible at this stage. We also find that as the EP becomes more professionalized over time, staffers are increasingly reluctant to reveal their social connections, thus emphasizing the great value of our data, even though it is imperfect.
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74 To refrain from inadvertently disclosing the identities of individual MEPs or staffers, we do not indicate national identity in the figure.
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77 Poole and Rosenthal, Congress: A Political-Economic History of Roll Call Voting, 1997
78 There is no theoretical reason to suspect that comparable levels of seniority will predict the tendency to vote alike. However, since estimates of standard errors for coefficients on dyadic variables tend to suffer from attenuation bias, leading to a high incidence of Type I error, it may be comforting to find no apparent significance where none is expected.
79 Antoine Tremblay, ‘LMER Convenience Functions: A suite of functions to back-fit fixed effects and forward-fit random effects, as well as other miscellaneous functions’, R package version 1.6.3, 2011, available at http://CRAN.R-project.org/package=LMERConvenienceFunctions.
80 Tremblay, ‘LMER Convenience Functions’, 2011
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81 Alternative specifications included a model with lagged votes as an independent variable and a model with joint membership in intergroups as an instrumental proxy. The data are sensitive to these specification changes; however, we find our current specification to be more theoretically consistent and valid than these alternatives. We also explored models with the reverse causality by estimating exponential random graph models with a dichotomous connectivity measure on the left-hand side. Such models, however, do not allow us to test our hypothesis about the conditional relationship between voting behaviour and social contact, based on ideology or anticipated agreement. We therefore find our current specification to be the best possible test of our theory.
* Department of Political Science, University of Wisconsin, Madison (email: email@example.com); Department of Public and International Affairs, George Mason University and Department of Political Science, University of North Carolina, Chapel Hill, respectively. The authors wish to thank the European Union Center at the University of Wisconsin for its support. They are grateful for data collection efforts and research assistance from Peter Truby, Katie Renze, Ashleigh Baker and Christina Boyes. They also thank Stacy Bondanella and Jean-Dominic LeGarrec for translating the survey into French, and Jason Koepke for his technical advice and assistance. They are grateful to Simon Hix for providing the EP roll-call vote data used in the analysis, and to Giacomo Benedetto for sharing the burden of processing the data. Finally, they thank David Canon, Scott Gehlbach, Elisabeth Gerber, Jonathan Hurwitz, Scott Morgenstern, Laura Wills Otero, three anonymous reviewers and the Journal's editor Hugh Ward for valuable comments and suggestions. The authors regret that they cannot make replication data publicly available, given the sensitivity of their data about the personal connections between political actors. All respondents were assured complete anonymity, and the small sample of (actual and potential) respondents prevents the release of data including general attributes such as party affiliation and nationality instead of proper names. Two Supplementary Appendices containing additional information are available online at: http://dx.doi.org/10.1017/S0007123412000518.
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