How Voting Rules Affect Expert Committee Deliberations and Decisions on Complex Problems

Complex and important policy decisions are often made with advice from a committee of experts, where experts first convene and discuss, before finalizing their collective decision with a vote. We show that the voting structure (whether the experts vote sequentially or simultaneously) plays a fundamental role in the nature of discussions, the independence of votes, and consequently the quality of the collective decision. Our context is the US Food and Drug Administration Advisory Committees' meetings, where experts evaluate the approvability of novel drugs and medical devices. We compile complete transcripts from 563 Advisory Committee meetings between 1999-2016 to study how a switch from sequential to simultaneous voting in 2007 changed the content and outcomes of committee meetings. We show that the change in voting structure improved the overall committee information-gathering and decision-making process. Specifically, simultaneous voting is correlated with: a reduction in the likelihood that a vote ended unanimously; committee discussions that focused more on information elicitation, rather than elaboration of existing information; less assertive, more positive, and more authentic language adopted by committee members; and improved decision accuracy, as evidenced by a reduction in the risk of drugs recommended for approval eventually being withdrawn from the market for reasons of safety and efficacy