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81 U. Chi. L. Rev. 131 (2014)
Expert Mining and Required Disclosure

handle is hein.journals/uclr81 and id is 137 raw text is: Expert Mining and Required Disclosure
Jonah B. Gelbacht
INTRODUCTION
In the social sciences, data mining sometimes refers pejo-
ratively to the repetitive use of classical statistical methods to
find evidence that results from only random variation.1 Vari-
ous aspects of evidence and civil-procedure law disincentivize
data mining by expert witnesses in federal civil litigation. But as
many authors have noted through the years, resourceful attor-
neys can do data mining's dirty work by hiring multiple experts,
asking each to provide an expert report on the same issue, and
then put on the stand only the one who provides the most favor-
able report.2 This practice is often referred to as expert shop-
ping or witness shopping.3 To emphasize its analogousness to
data mining, though, I will use the term expert mining.
Nothing in the Federal Rules of Evidence or the Federal
Rules of Civil Procedure (jointly, the Rules) prevents expert
t Associate Professor, University of Pennsylvania Law School. I thank Steve Bur-
bank, Richard Epstein, Anup Malani, David Marcus, Kathryn Spier, and Tobias Barring-
ton Wolff for helpful comments and suggestions.
1 For example, one might run many statistical models on the same data set, vary-
ing the included explanatory variables to find the greatest possible value of conventional
test statistics, as Stata's built-in stepwise command does automatically. See Stata 13
Help for Stepwise, Stata (StataCorp LP 2013), online at http://www.stata.com/
help.cgi?stepwise (visited Mar 2, 2014). The term data mining has a more neutral
meaning in other fields, especially computer science. See, for example, Wikipedia, Data
Mining, online at http://en.wikipedia.org/wiki/Datamining (visited Mar 2, 2014). Other
terms sometimes used to distinguish the pejorative version include data snooping, see
Halbert White, A Reality Check for Data Snooping, 68 Econometrica 1097, 1098 (2000),
and data dredging, see Wikipedia, Data Dredging, online at http://en.wikipedia.org/
wiki/Datadredging (visited Mar 2, 2014).
2 See Samuel R. Gross, Expert Evidence, 1991 Wis L Rev 1113, 1143; Richard A.
Posner, An Economic Approach to the Law of Evidence, 51 Stan L Rev 1477, 1541-42
(1999); Richard A. Posner, The Law and Economics of the Economic Expert Witness, 13 J
Econ Persp 91, 98 (Spring 1999); Christopher Tarver Robertson, Blind Expertise, 85
NYU L Rev 174, 211 (2010).
3 See, for example, Posner, 51 Stan L Rev at 1541-42 (cited in note 2) (referring to
witness shopping); Andrew MacGregor Smith, Note, Using Impartial Experts in Valua-
tions: A Forum-Specific Approach, 35 Wm & Mary L Rev 1241, 1247 (1994) (explaining
expert shopping).

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