Social Networks and the Geography of Voting: A Spatial Econometric Approach

本论文探讨社交网络的地理结构与选举结果之间的关系。它利用空间分析，计量经济学方法和不同地方人口之间社会联系密度的数据，为社会科学中的一系列相关文献做出实证贡献。本文由引言、三个独立的实证章节和结论组成。所有三章的共同主题是观察到非本地，甚至地理上遥远的社会关系可以在塑造当地投票行为方面发挥重要作用。在第一章中，我调查了2016年英国欧盟成员国公投中与贸易相关的就业冲击对投票选择的影响。从英国选举研究中的国际领土3级（ITL3）地区和个人层面的投票数据来看，我研究了不同地方劳动力市场冲击的区域社会接近度是否影响了对休假选择的支持。工具变量估计数表明，对投票行为的社会溢出效应与区域内接触和旅行平均距离为74至102公里的影响相当。在第二章中，我考察了美国地方推出的全邮寄投票政策对投票方式选择的社会溢出效应。结合北卡罗来纳州整个选民的个人层面行政记录和各州邮政编码制表区（ZCTA）之间的社会关系数据，我研究了政策转换司法管辖区的社会关系份额如何影响2020年美国总统大选的邮件投票。差异中的差异估计数显示了积极的溢出效应，主要来自2 000公里以外人口众多的西方管辖区。在第三章中，我探讨了2020年美国总统大选中党派同质性的地理分布。我用当地的莫兰指数，以确定集群的政治同性恋ZCTA和研究他们的特点。研究结果表明，虽然党派同性恋的空间模式广泛跟踪居住隔离沿着城乡连续体，有显着的党派差异的相对密度和地理距离的社会关系：同性恋民主党倾向的地区可能有更密集和更遥远的关系比同性恋民主党倾向的地区。总的来说，本论文为社会互动在选举中的作用及其与公共政策的联系提供了新的证据。

This thesis examines the relationship between the geographic structure of social networks and electoral outcomes. It draws on spatial analysis, econometric methods, and data on the density of social ties between the populations of different places to make empirical contributions to a body of related literatures in the social sciences. The thesis is comprised of an introduction, three independent empirical chapters, and a conclusion. The common theme uniting all three chapters is the observation that non-local, and even geographically distant social ties can play an important role in shaping local voting behaviour. In the first chapter, I investigate the effect of social proximity to trade-related employment shocks on vote choice in the 2016 UK EU membership referendum. Looking at referendum results in International Territorial Level 3 (ITL3) regions and individual-level voting data from the British Election Study, I examine whether regional social proximity to shocks in different local labour markets affected support for the Leave option. Instrumental variable estimates suggest that social spillover effects on voting behaviour are comparable to those of within-region exposure and travel an average distance of 74 to 102 kilometres. In the second chapter, I examine social spillovers on choice of voting method from local rollouts of all-mail voting policy in the United States. Combining individual-level administrative records on the entire electorate of North Carolina and data on the social ties between zip code tabulation areas (ZCTAs) across states, I look at how the share of social ties in policy-switching jurisdictions affected mail voting in the 2020 US presidential election. Difference-in-differences estimates are indicative of positive spillover effects, primarily originating from populous Western jurisdictions located over 2,000 kilometres away. In the third chapter, I explore the geography of partisan homophily in the 2020 US presidential election. I use the local Moran index to identify clusters of politically homophilous ZCTAs and examine their characteristics. The findings suggest that while spatial patterns of partisan homophily broadly track residential segregation along the urban-rural continuum, there are notable partisan differences in the relative density and geographic distance of social ties: homophilous Democratic-leaning areas are likely to have denser and more distant ties elsewhere than homophilous Republican-leaning areas. Overall, the thesis contributes new evidence on the role of social interactions in elections and its links to public policy.