Whose Bread I Don’t Eat, His Song I Don’t Sing? MPs‘ Outside Earnings and Dissenting Voting Behaviour

The question whether outside earnings of politicians have an effect on their political behaviour is part of a lively public debate about the quality of representative democracy. However, the scholarly focus mainly rests on the impact of moonlighting on the amount of participation in legislative activities by members of parliament (MPs). Whether or not MPs with high outside earnings differ from their colleagues regarding their actual voting behaviour has neither been theorized nor empirically examined yet. Although party unity is a common feature of parliamentary democracies and voting against the party line is a rare phenomenon, quite substantial variation can be observed among both the MPs and the roll-call votes. Referring to different pathways to party unity previously established in the literature, I argue that MPs with high outside earnings at large are not expected to have a higher level of policy disagreement with or less loyalty towards their party. But owing to a higher degree of financial and career-related independence, they can be less effectively disciplined by their party by appealing to office seeking incentives than their counterparts with no or negligible sideline earnings. Hence, it is hypothesized that MPs with high outside earnings have a higher probability to vote against the party line. This proposition is tested quantitatively using multi-level logistic regressions and considering a battery of controls at both the MP and roll-call vote level to explain more than 115,000 individual voting decisions in the German Bundestag (2013-2017). The findings have important implications for our understanding of the link between politicians’ career paths and political behaviour as well as for the study of parliamentary representation.