A Big Data, Machine-Learning History of Early English Caselaw and Legal Ideas
Peter Grajzl - Washington and Lee University;
Peter Murrell - University of Maryland
-- The history of English law is to a great extent a history of caselaw. Yet the historical development of English caselaw and its associated legal ideas remains incompletely understood. In our two-part study, “A machine-learning history of English caselaw and legal ideas prior to the Industrial Revolution,” published in two issues of the Journal of Institutional Economics (Part I here and Part II here), we use quantitative tools for analysis of text-as-data to study the development of English caselaw prior to the Industrial Revolution.
Systematic study of ideas embodied in court decisions is difficult due to the multiplicity of elements that make up caselaw and the fact that court decisions do not readily lend themselves to conventional quantitative analysis. To address these challenges, we first build a comprehensive corpus of tens of thousands of reports on cases heard in England's high courts during the late medieval and early modern era. Leveraging the information in these case reports, we then use machine-learning methods to identify the salient ideas embodied in the corpus and to characterize the key patterns in the temporal evolution of these ideas.
To aid in the understanding of the temporal patterns found in the data, we present a stylized model of the diffusion of legal ideas. The model clarifies that the attention to a set of legal ideas at any given point in time reflects the amount of change in the adherence to the corresponding legal ideas. Conceptually, the notion of attention corresponds to the rate of infection in an epidemiological model, while the cumulative amount of attention up to a certain time corresponds to the cumulative number of infections by that time. (Thus the model of attention and development of new ideas is very similar to the model of the spread of a new virus.)
Drawing on the resulting framework, we first provide a bird's-eye view of the development of early English caselaw and associated legal ideas. Procedure is the highest-prevalence theme in the corpus, but by the mid-18th century attention to procedure decreases sharply, an indication of the solidification of court institutions. Important ideas on real-property were substantially settled by the mid-17th century and on contracts and torts by the mid-18th century. Crucial elements of English caselaw therefore developed before the Industrial Revolution.
We next examine the legal ideas associated with England's financial revolution. That the latter occurred before the Industrial Revolution is well understood. But there is controversy about the time-periods during which the financial revolution took place, whether institutional changes spurred the financial revolution, and, if so, which institutions were important. The focal point of the controversy has been a hypothesis that the constitutional changes consequent on the Glorious Revolution of 1688 led to increased government credibility and subsequent changes in credit markets. Casting light on this issue, our empirical evidence shows that many new legal ideas pertinent to finance were well accepted long before the Glorious Revolution. Moreover, since these legal ideas were generated within decisions on real disputes reaching the courts, the financial revolution itself, in terms of the practices of real economic actors, was a development of the whole 17th century and not exclusively, or even predominantly, a by-product of political and constitutional events at the century's end.
Finally, we examine the evolution of ideas pertinent to the sources of law used in the courts. Our estimates reveal that precedent-based reasoning was not a prominent part of English caselaw prior to 1600. Ideas on precedent-based reasoning are featured more prominently after 1650, but diffuse very gradually, and solidify only after 1700. One of the central characteristics of English legal reasoning gained widespread acceptance in the legal profession at a relatively late date.