Chapter 93 Structure Induced Equilibrium in Spatial Committee Games Markets auction mechanisms and political institutions all affect outcomes. For students of collective choice minimal decision making institutions provide a baseline by which we expect outcomes that best can be characterized as chaotic. Such outcomes are rarely predictable and the processes by which they are selected are marked by voting cycles and drifting through the alternative space. More interesting for collective choice theorists are those mechanisms introduced into a minimal institutional setting that in turn brings predictability to outcomes. Almost all institutions charged with making collective choices are richly layered with rules. The United States House of Representatives is one of the more rule bound institutions that has been studied extensively and empirical scholars take for granted that its outcomes will be predictable and patterned. However disentangling which structural features matter and when they matter remains a task for theorists. Experimentalists continue to offer examples as to when institutions matter.