Analyses of voting algorithms often overlook informational externalities shaping individual votes. For example, pre-polling information often skews voters towards candidates who may not be their top choice, but who they believe would be a worthwhile recipient of their vote. In this work, we aim to understand the role of external information in voting outcomes. We study this by analyzing (1) the probability that voting outcomes align with external information, and (2) the effect of external information on the total utility across voters, or social welfare. In practice, voting mechanisms elicit coarse information about voter utilities, such as ordinal preferences, which initially prevents us from directly analyzing the effect of informational externalities with standard voting mechanisms. To overcome this, we present an intermediary mechanism for learning how preferences change with external information which does not require eliciting full cardinal preferences. With this tool in hand, we find that voting mechanisms are generally more likely to select the alternative most favored by the external information, and when external information reflects the population's true preferences, social welfare increases in expectation.

翻译：关于投票算法的分析常常忽视塑造个体投票行为的信息外部性。例如，民调信息往往使选民倾向于并非其首选、但被认为值得投出选票的候选人。本研究旨在理解外部信息在投票结果中的作用。我们通过分析以下两点展开研究：（1）投票结果与外部信息一致的概率，以及（2）外部信息对选民总效用（即社会福利）的影响。在实践中，投票机制仅能获取选民效用的粗略信息（如序数偏好），这首先阻碍了我们直接运用标准投票机制分析信息外部性的影响。为克服这一障碍，我们提出了一种中介机制，该机制无需获取完整的基数偏好即可学习偏好如何随外部信息变化。借助这一工具，我们发现：投票机制通常更可能选择外部信息最支持的备选方案；当外部信息反映群体真实偏好时，社会福利的期望值将会提升。