Buying Supermajorities in the Lab

Many political decisions are taken in legislatures or committees and are subject to lobbying efforts. A seminal contribution to the vote-buying literature is the legislative lobbying model pioneered by Groseclose and Snyder (1996), which predicts that lobbies will optimally form supermajorities in many cases. Providing the first empirical assessment of this prominent model, we test its central predictions in the laboratory. While the model assumes sequential moves, we relax this assumption in additional treatments with simultaneous moves. We find that lobbies buy supermajorities as predicted by the theory and supporting evidence for the comparative statics predictions with respect to lobbies' budgets and legislators' preferences. Some comparative statics effects also carry over to the simultaneous move set-up but the predictive power of the model is much weaker.