Exploring the U.S. corporate connectivity in 1997–2015: drivers and patterns of multilayer network evolution

American companies are connected in numerous ways, and these interorganizational networks affect how companies compete, innovate, and exert pressure in the political realm. Yet where do networks themselves come from? Moreover, do they stay stable or change? Just as people can connect through friendship or job, firms can have qualitatively distinct network ties. This thesis explores the origins and the dynamics of four different modes of interfirm connectivity: board interlock between companies who share the same director serving on their boards, alliance (a long-term business collaboration), investor interlock between two companies whose stock is held by the same investor, and a tie through executive migration between two firms.

Past research shows that various factors matter for corporate networks (e.g., charismatic managers, market uncertainty, or industry trends). Chapter 1 asks how much or how little each of them matter compared to other factors. For example, alliance network depends largely on industry, but geographical location is most important for board interlocks. Chapter 2 explores how current ties affect future ones. In particular, new alliances do not depend much on existing structures network, but ties via executive migration do. Chapter 3 examines changes in the multilayer corporate network from 1997 to 2015: while alliance and board interlock connections declined, investor interlock ties grew rapidly. The results demonstrate that, when asking how networks form, develop, and influence organizations and society, it is important to consider the mode of connectivity. Exploration of different tie types generates distinct insights into the nature of corporate networks.