Intermediation, Information, and Diversity in Networks

在经济和社会背景下，网络无处不在。个人决策和福利受到本地连接以及全球网络架构的影响。这项由该奖项资助的研究调查了代理人相互作用的网络如何影响各种市场和团体活动的结果。有三个截然不同的项目。前两部分考察了网络结构对贸易中介和信息扩散的影响。第三个项目考察哪些网络特征对于在社会影响的选择中保持多样性至关重要。第一个项目研究网络中的中介作用。该理论表明，卖家的利润不仅取决于交易路径上中间商的数量，还取决于每个中间商提供的接触买家的竞争路径的完整集合。卖家更喜欢沿着转售价值相似的中介机构之间存在本地竞争的路径进行交易。交易路径不一定最小化中介或最大化福利。将网络分解为多层中介权力是均衡转售利润的特征。本地竞争在层内被利用，而跨层交易中出现了拖延问题。这项研究对于打击有组织犯罪和非法贸易，防止等级结构中的腐败，以及供应链中的高效生产具有重要意义。第二个项目调查信息(技术创新、研究想法、新闻和八卦)如何定价以及如何在网络链接上传播。与对中介的研究不同，信息好是非竞争的；任何获得好的玩家随后可以将其复制并转售给任意数量的不知情的邻居。初始信息源在网络中的位置影响行为者从获取和转售信息中获得的利润，并影响扩散过程。卖家为争夺客户而竞争，并在网络中建立个人影响力范围。其主要目标是证明利润被限制在某个网络分区的块内。与同一区块内的端点的链接构成了瓶颈，并在获取利润方面发挥着重要作用。跨越区块的链接在连接网络方面并不关键，并会给卖家带来负面外部性。第三个项目考虑了这样一种设置，即处于网络中的玩家需要采取行动或形成与大多数邻居一致的意见。对任何特定行动的一致协调构成了一种平衡。许多网络还具有具有不同行动选择的均衡。这项研究的目的是刻画在最佳响应动态中引入随机突变时多样性具有健壮性的网络。本研究中开发的工具和方法将提供更广泛的影响，使公司和政策制定者能够更好地了解网络关系如何影响市场结果。

Networks are ubiquitous in economic and social contexts. Individual decisions and welfare are affected by local connections, as well as by global network architecture. The research funded by this award investigates how the networks in which agents interact influence outcomes in a variety of market and group activities. There are three distinct projects. The first two investigate the impact of network structure on trade intermediation and information diffusion. The third project examines what network features are essential for the persistence of diversity in socially influenced choices.The first project studies intermediation in networks. The theory suggests that the seller's profit depends not only on the number of middlemen along the path of trade, but also on the complete collection of competing paths of access to buyers offered by each middleman. The seller prefers to trade along paths that entail local competition among intermediaries with similar resale values. Trading paths do not necessarily minimize intermediation or maximize welfare. A decomposition of the network into layers of intermediation power characterizes equilibrium resale profits. Local competition is exploited within layers and hold-up problems arise in transactions across layers. This research has implications for combating organized crime and illegal trade, preventing corruption in hierarchical structures, and efficient production in supply chains. The second project investigates how information (technological innovations, research ideas, news and gossip) is priced and diffused across the links of a network. In contrast to the research on intermediation, the information good is non-rival; any player who gets possession of the good may subsequently replicate and resell it to an arbitrary number of uninformed neighbors. The positions of the initial sources of information in the network affect the profits that actors accrue from acquiring and reselling the information and shape the diffusion process. Sellers compete for customers and establish individual spheres of influence in the network. The main objective is to prove that profits are confined within the blocks of a certain network partition. Links with endpoints within the same block constitute bottlenecks and play an important role in extracting profits. Links bridging across blocks are not critical in connecting the network and impose negative externalities on sellers. The third project considers a setting where players situated in a network need to take actions or form opinions that conform with a majority of their neighbors. Unanimous coordination on any particular action constitutes an equilibrium. Many networks also feature equilibria with diverse action choices. The aim of this research is to characterize the networks for which diversity is robust to the introduction of stochastic mutations in the best response dynamic. The tools and methods developed in this research will provide broader impact by allowing firms and policymakers to better understand how network relationships affect market outcomes.