H.B. Keller Colloquium

In many social and economic settings, decisions of individuals are affected by the actions of their friends, colleagues, and peers. Examples include adoption of new products and innovations, opinion formation and social learning, public good provision, financial exchanges and international trade. Network games have emerged as a powerful framework to study these settings with particular focus on how the underlying patterns of interactions, governed by a network, affect the economic outcomes. For tractability reasons, much of the work in this area studied games with special structure (e.g., quadratic cost functions, scalar non-negative strategies) or special properties (e.g., games of strategic complements or substitutes).

In this talk, we first present a unified framework based on a variational inequality reformulation of the Nash equilibrium to study equilibrium properties of network games including existence and uniqueness, convergence of the best response dynamics and comparative statics. Our framework extends the literature in multiple dimensions, covering games with general strategic interactions and multidimensional and constrained strategy sets. In the second part of the talk, we will present a new class of infinite populations games, graphon games, that can capture heterogenous local interactions. We will show that equilibria in graphon games can approximate the equilibria of large network games sampled from the graphon. We also show that (under some regularity assumptions on the graphon), interventions based on graphon games can be designed using computationally tractable optimization problems and with much less information than the entire network structure.