Institutional Lock-in: The Self-Reinforcing Suppression Mechanism After Familiar Route Depth Exceeds Threshold in Social Fields

Drawing on sedimentation field dynamics, this paper defines institutional lock-in as a dynamic inevitability that emerges once an institution’s Familiar Route depth (Familiarity) and flow-share proportion (FlowShare) jointly exceed their respective lock-in thresholds — at which point the institution actively suppresses the generation of alternative structures, rather than merely persisting through inertia or interest-group protection. The central claim is: reform that does not change Familiar Routes does not change institutions. Any reform attempt below the replacement threshold (T_replace) will not only fail but trigger rebound, leaving the institution harder to change than before. The paper derives the institutional lock-in operator (Lock), the replacement cost equation (RepCost), the self-reinforcing loop, three levels of lock-in (soft, hard, deep), and three theorems (Lock-in Inevitability, Reform Rebound, Deep Lock-in Directional Constraint). All propositions are accompanied by breakdown conditions.