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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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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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