Path Dependence in the Law: The Course and Pattern of Legal Change in a Common Law System

Part I of this Article provides an overview of path dependence theory. It outlines the theory and briefly describes three separate strands of the theory: increasing returns path dependence, evolutionary path dependence, and sequencing path dependence, which are rooted in the economics, biological, and rational choice theory literatures, respectively. Although each of these strands has specific and unique characteristics, they are linked by a central insight: In each, an outcome or decision is shaped in specific and systematic ways by the path leading to it. Each of these strands of path dependence in turn has important implications for the course and pattern of change in the common law system. Accordingly, Part II applies path dependence theory to the common law. At the core of the common law system is the requirement that courts adhere to the body of principles and rules of action that derive their authority "solely from usages and customs of immemorial antiquity, or from the judgments and decrees of the courts recognizing, affirming, and enforcing such usages and customs." Under the doctrine of stare decisis, higher courts' previous decisions are controlling, courts give their own decisions significant weight, and courts look to non-binding decisions for persuasive precedent. Consequently, although there is some flexibility in the system, precedent remains central to legal deliberation. The doctrine of stare decisis thus creates an explicitly path-dependent process. Later decisions rely on, and are constrained by, earlier decisions. More important, the way in which history shapes legal outcomes corresponds to the three-fold division introduced in Part I. Because each legal decision increases the probability that the next will take a particular form, the common law exhibits increasing returns path dependence. Because the law changes through a process of punctuated yet historically constrained evolution, the common law exhibits evolutionary path dependence. And because the legal process involves sequential decisionmaking in a process marked by competing alternatives and multiple actors, the common law exhibits sequencing path dependence. Therefore, just as biological and social processes are constrained by history, the law is firmly guided by the heavy hand of the past. Finally, Part III turns from the descriptive to the normative. It analyzes the implications of path dependence theory for the doctrine of stare decisis. Path dependence theory reveals that significant costs may arise out of the reliance on precedent in a common law system. The Article concludes with the claim that, all other things being equal, where the costs of path dependence are expected to be especially significant, courts should consider relaxing the doctrine of stare decisis. This prescription not only supports modifying existing practices of reliance upon precedent, but also provides a theoretical basis for some existing distinctions in the degree that judges rely on certain categories of precedent.