Analogical Legal Reasoning: Theory and Evidence

Abstract:     
How do judges reason about the law? The canonical theory is that they reason by analogy from case to case. According to critics, however, the theory is at best indeterminate and at worst a fantasy. This paper has two objectives. The first objective is to offer a formal model of analogical legal reasoning (ALR). I model ALR as similarity-weighted averaging. Under the model, the outcome in the present case is a weighted average of the outcomes of prior cases, where the weights depend on fact similarity (distance in fact space) and precedential authority (position in the judicial hierarchy). The second objective is to take the model to data. The empirical analysis suggests that the ALR model is a plausible model for the time series of U.S. maritime salvage cases. I conclude by discussing the academic debate over ALR and arguing that formal models of legal reasoning offer a way forward.

Number of Pages in PDF File: 38

Keywords: analogical legal reasoning, case-based decision theory, empirical similarity, jurisprudence

JEL Classification: K00, K10, K49

working papers series