Division of Labour and Dissenting Voting Behaviour of MPs in a ‘Working Parliament’

The question of why the probability of votes against the party line differs among members of parliament (MPs) and legislative motions is part of a growing literature within parliamentary research. Whereas discipline-related as well as electoral reasons have been repeatedly discussed, another factor has remained largely neglected in the literature: division of labour within parliamentary party groups. Given the workload and the high level of specialization of parliamentary work, MPs usually engage in a few committees and the corresponding bodies of their party group and, therefore, are concerned with only a subset of all policies in detail. This leads to conflicting expectations with regard to their voting behaviour on the floor: On the one hand (policy-shaping hypothesis), MPs might have a lower probability to defect in votes on matters *within* their policy area of expertise since they are familiar with the contents of those motions and, presumably, even had the opportunity to shape their party group’s policy position – in accordance with their own one. On the other hand (cue-taking hypothesis), MPs might have a lower probability to defect in votes on matters *beyond* their policy area since it appears rational for them to simply adhere to the policy specialists of their party group and, thereby, conform to the division of labour principle. Both hypotheses are tested quantitatively using roll-call vote data of a powerful ‘working parliament’, the German Bundestag. The results have implications for our understanding of MPs’ parliamentary behaviour, the functioning of parliamentary party groups as well as for research on parliamentary committees.