Three Essays on Networks


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Virginia Tech


This dissertation consists of three essays studying human behavior and contagion phenomenon in networks. The analysis especially focuses on information sharing, trade relationship and pest spread in networks. The first chapter outlines the dissertation by briefly discussing the motivations, methods, and main findings in each of the following chapters.

Chapter two examines the information sharing in networks. We develop a heterogenous agents model in which connections between players act as a channel to exchange information. We focus on specialized equilibria, which is based on Nash tatonnement. It is shown that players utilize the signals in the linear form and only specialized equilibria can be stable. We also compare the sequential equilibria and stable equilibria, and it is shown that stable equilibria form a proper subset of the sequential ones, which gives a sharper prediction. The stable equilibria demonstrate star-like graphs, which is similar to the phenomenon "the law of the few" in the literature.

Chapter three investigates the trade relationship among players where trade between two players can bring benefits as well as conflict. And if conflict happens, the players coordinate based on received information. We show that the optimal structure of trade networks ranges from complete market to Autarky. Also, we study the optimal timing for trade relationship establishment and the optimal size of organizations when facing scarce members. It is shown that when potential neighbors become more scarce, people care more about the future, or new technology breakthroughs occur more frequently, it is optimal to have more neighbors to back up for the potential technological breakthrough.

The last chapter studies the pest spread in the networks. We use a directional and weighted network to study the spread of Tuta absoluta. A robust network-based approach is proposed to model seasonal flow of agricultural produce and examine its role in pest spread. Furthermore, the long-term establishment potential of the pest and its economic impact on the country are assessed. Preliminary analyses indicate that Tuta absoluta will invade most major tomato production regions within a year of introduction and the economic impact of invasion could range from $17-25 million.



Network, Information, International Trade, Contagion