Neglect the Base Rate: It's the Law!

18 Pages Posted: 23 Dec 2012

See all articles by Christoph Engel

Christoph Engel

Max Planck Society for the Advancement of the Sciences - Max Planck Institute for Research on Collective Goods; University of Bonn - Faculty of Law & Economics; Erasmus University Rotterdam (EUR), Erasmus School of Law, Rotterdam Institute of Law and Economics, Students; Universität Osnabrück - Faculty of Law

Date Written: December 1, 2012

Abstract

If accurate prediction is the goal, and if information about the unconditional probability of the predicted event is available, a strong case can be made for using this information, i.e. for a Bayesian approach to inference. Not so rarely, the law calls for accurate prediction, e.g. if a bailing decision hinges on an estimate of recidivism risk. Yet for other questions of law, and for the law of evidence in particular, accuracy is not the exclusive goal. Substantive law determines who should bear the risk that doubt cannot be removed. These rules decide whether several individuals, or several acts for that matter, shall be treated as members of a class. Applying Bayes’ rule also implicitly treats the person or the action in question as a member of a class. If in conflict, the normative decision of substantive law overrides Bayes’ rule, and forces judges and administrators to neglect the base rate.

Keywords: base rate, Bayes’ rule, acting in concert, product share liability, alternative causes

Suggested Citation

Engel, Christoph, Neglect the Base Rate: It's the Law! (December 1, 2012). MPI Collective Goods Preprint, No. 2012/23. Available at SSRN: https://ssrn.com/abstract=2192423 or http://dx.doi.org/10.2139/ssrn.2192423

Christoph Engel (Contact Author)

Max Planck Society for the Advancement of the Sciences - Max Planck Institute for Research on Collective Goods ( email )

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University of Bonn - Faculty of Law & Economics

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Erasmus University Rotterdam (EUR), Erasmus School of Law, Rotterdam Institute of Law and Economics, Students ( email )

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Universität Osnabrück - Faculty of Law

Osnabruck, D-49069
Germany

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