Decades of Jurimetrics (2001.00476v1)

Abstract: Jurimetrics: decades of history, decades to-be auspicious. A Brazilian point of view on the trajectory of this forgotten concept in the quantitative approach of the law, with code and examples in free software.

• The paper outlines the evolution of Jurimetrics from early quantitative legal thought to modern data-driven legal applications.
• It introduces a three-prism framework for judges, lawmakers, and lawyers that integrates statistical methods and Bayesian analysis.
• The study demonstrates practical use cases with free software and R package examples, highlighting tools for predictive legal analytics.

This paper, "Decades of Jurimetrics" (2001.00476), provides a historical overview and practical guide to Jurimetrics, defined as the application of quantitative methods to law. It traces the intellectual lineage of this field, arguing that while the term was coined by Lee Loevinger in 1949, the underlying ideas date back centuries.

Historical Context and Loevinger's Contribution:

• The paper establishes a long history of quantitative legal thought, citing figures like Leibniz (17th century), Nicolas Bernoulli (1709, applying probability to legal issues), Condorcet (1785, Jury Theorem), Quetelet, Guerry, and Poisson (19th century, analyzing crime statistics).
• It highlights Oliver Wendell Holmes Jr.'s emphasis on experience and prediction ("The life of the law has not been logic: it has been experience," "The man of the future is the man of statistics...").
• Lee Loevinger is presented as the key figure who synthesized these ideas and formally proposed "Jurimetrics" in 1949 as the "next step forward" from jurisprudence (speculation about law) to the scientific investigation of legal problems.
• Loevinger's work (spanning 1949-1992) advocated for:
  • Rationality and scientific methods (logic, statistics, probability) in law.
  • Moving beyond the "individualized case" focus of Legal Realism towards identifying general principles.
  • Using Bayesian probability to update beliefs based on evidence (data).
  • Early recognition of the potential of electronic data retrieval and analysis, distinguishing between "hardware" and "software."
  • Applying statistical concepts like association factors (Stiles) and probabilistic indexing (Maron) to legal texts.
• The paper notes a divergence where modern "Empirical Legal Studies" (ELS) literature often overlooks Loevinger and the term "Jurimetrics," despite significant overlap. It speculates this might stem from Loevinger's sometimes critical stance towards the legal profession's resistance to scientific methods.

The Three Prisms of Jurimetrics:

The authors propose a framework (originally from Zabala & Silveira, 2014) to understand jurimetrics through the perspectives of the judiciary's main actors:

1. The Judge: Using quantitative methods for decision support (optimal decisions, utility theory), evaluating expert testimony, incorporating precedents, and Bayesian updating of opinions (e.g., assessing moral damage indemnity values).
2. The Lawmaker: Crafting data-driven legislation, conducting regulatory impact analyses (now mandated in Brazil by the Economic Freedom Act), forecasting judicial system load (e.g., case volume), identifying systemic issues (e.g., studying child adoption processes or identifying "biggest litigants" to find alternative solutions).
3. The Lawyer: Supporting arguments quantitatively (e.g., demonstrating potential losses for injunctions), assessing probabilities of success, predicting outcomes, managing case portfolios, estimating financial provisions for lawsuits, compliance risk assessment, and utilizing Alternative/Online Dispute Resolution (ADR/ODR) and smart contracts.

Practical Applications and Tools:

• The paper emphasizes practical implementation using free software (R, Python, Stan, LaTeX, etc.) and reproducibility (citing the Science Code Manifesto).
• Several specific examples are mentioned:
  • Hand Rule (cost-benefit analysis for liability).
  • Paternity probability calculations using Bayesian methods and Hardy-Weinberg equilibrium.
  • Analysis of leasing contracts using Bayesian calculators.
  • Assessing randomness in judicial case assignment.
  • Identifying norm conflicts in contracts using logic and NLP.
• Two detailed examples are provided using the authors' jurimetrics R package:
  • Preliminary Injunction Loss Calculation: An exp_loss function calculates the expected daily financial loss for a company wrongly listed on a credit bureau, quantifying the "danger in delay."
  • ```R
  • # Example Usage (Conceptual)
  • library(jurimetrics)
  • ev <- exp_loss(average.consult = 1000, prob.hire = 0.1, average.ticket = 3450)
  • print(ev$expected.loss)</li> <li>print(ev$text)

  • * **Court Proceedings Volume Forecast:** Using time series data (monthly TJRS court lawsuits from 2000-2017), the `fits` function automatically compares ARIMA, ETS, TBATS, and NNETAR models based on prediction Mean Squared Error (MSE) on a test set, selects the best model, and generates forecasts.

    R
  • # Example Usage (Conceptual)
  • library(jurimetrics)
  • data(tjrs_year_month)
  • y <- ts(data = tjrs_year_month$count, start = c(2000,1), frequency = 12)</li> <li>fit &lt;- fits(y, steps = 43) # Forecast 43 steps ahead</li> <li>print(fit$best.model)
  • print(fit$fcast)
  • # plot(fit) # Visualizes the forecast
  • ```

Challenges and Conclusion:

• The paper contrasts Brazil's Access to Information Act (which mandates open, machine-readable data access) with the practical difficulties the authors faced in obtaining usable judicial data from official channels. This is juxtaposed with a recent French law imposing heavy penalties for analyzing or predicting individual magistrates' practices.
• It concludes with a section titled "The Posterior Step," using a nursery rhyme and the story of Bellerophon to illustrate Bayesian reasoning – how subjective probabilities (beliefs) are sequentially updated as new evidence (information) becomes available. The final "evidence" presented is Karl Llewellyn's book "The Bramble Bush," leaving the reader to consider its impact.

In essence, the paper argues for the recognition and adoption of Jurimetrics as a vital, scientifically grounded approach to understanding and improving legal systems, providing historical context, a practical framework (the three prisms), and concrete tools and examples while acknowledging data access challenges.