Are courts more likely to suppress civil liberties in times of war? Does a judge's gender influence his or her decisions? Do independent judiciaries promote economic freedom? Answering such questions calls for empirical evidence, and arguments based on empirical research have become an everyday part of legal practice, scholarship, and teaching. In litigation judges are confronted with empirical evidence in cases ranging from bankruptcy and taxation to criminal law and environmental infringement. In academia researchers are increasingly turning to sophisticated empirical methods to assess and challenge fundamental assumptions about the law.

As the role of empirical methods in traditional legal scholarship and practice grows, new forms of education are needed for today's lawyers. All lawyers asked to present or assess empirical arguments need to understand the fundamental principles of social science methodology that underpin sound empirical research. This book presents that methodology in a legal context, explaining how empirical analysis can inform legal arguments; how lawyers can set about framing empirical questions, conducting empirical research, analyzing data, and presenting or evaluating the results. The fundamentals of understanding data, statistical models, and the structure of empirical arguments are explained in a way accessible to lawyers with or without formal training in statistics.

Written by two of the world's leading experts in empirical legal analysis, drawing on years of experience in training lawyers and academics in empirical methods, this book will be an invaluable primer for all students, academics, or practicing lawyers coming to empirical research— whether they are embarking on an empirical research project, or engaging with empirical arguments in their field of study, research, or practice.

The book is available from the following merchants:
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To claim that research based on data—that is, empirical work—has infiltrated the legal community borders on the boring.1 Social scientists and historians have long brought data to bear on the study of law and legal institutions.2 In ever-increasing numbers, legal academics throughout the world are following suit.3

But it's not only academics who are making greater use of data-based evidence in their research. Arguments following from empirical studies have become such a regular part of legal practice that lawyers (and law students!) neglect learning about methods for collecting and analyzing data at their own peril. We could say the same of judges who are all too often confronted with data or the results of empirical studies in cases ranging from bankruptcy to criminal law to environmental infringement to taxation.4 As Oliver Wendell Holmes famously wrote, "For the rational study of the law the black letter man may be the man of the present, but the man of the future is the man of statistics and the master of economics."5 That future is here.6

And yet there is no book designed to provide members of the legal community with a sufficient introduction to empirical legal work so that they can evaluate existing studies, become conversant in basic statistical methods, begin to undertake investigations of their own, or all of the above.7 Hence An Introduction to Empirical Legal Research—a book explicitly for law students, lawyers, judges, and scholars interested in law and legal institutions.

In producing An Introduction to Empirical Legal Research we drew heavily on materials we developed for an annual empirical workshop for law professors, courses we offer to law students, and a day-long educational program for judges. We also made liberal use of the handful of articles we have written on designing, executing, and presenting the results of statistical studies.8

Throughout our courses and articles we bring in many practical examples. Some are of our own devising, others come from existing empirical studies, and still others from court cases. No matter the source, we go beyond mere description; we make use of data so that our students and readers can experience the research process for themselves. This is extremely important here too. Regardless of whether you are reading An Introduction to Empirical Legal Research to consume or produce empirical studies, only by understanding the process will you be able to decipher its products—including scholarly articles, consultants' reports, and expert testimony.9

For readers hoping to learn enough about these products so that they can follow and evaluate them, working through the examples in the book may be sufficient. For those desiring to execute empirical studies, the book's website houses the tools necessary to replicate and expand the examples in the book.10 In particular, you'll find:

Datasets. For each dataset we use in the book, we've created a compre- hensive codebook and a downloadable data file in various formats (comma delimited text, Stata, SPSS Portable, R Data Format, SAS Transport, and Microsoft Excel).

Introduction to Statistical Software. We provide introductions to two different packages: Stata11 and R.12 The introductions include step-by-step written documentation and video demonstrations of both packages.

Chapter-by-Chapter Command Files. Along with the datasets, the command files enable the reader to replicate (in Stata or R) every analysis in the book.

"Best Practices" Guide. This guide should help ensure that research employing R or Stata not only makes effective use of the software but also conforms to standard operating procedures in the field.

References. The website provides a list of some of our favorite books on research design, data collection methods, and statistics. It also includes links to datasets that you might find useful for law-related projects.

One final note. It's important to keep in mind the first two words of the book's title. We do indeed conceptualize An Introduction to Empirical Legal Research as a primer. Mastering all the topics we cover requires far more than we can possibly convey here; it requires training. That's why Ph.D. programs in the social sciences not only offer basic introductions to research design and statistics but also courses devoted to particular types of methods—maximum likelihood estimation, time series analysis, and structural equation models, to name just a few. Our goal is to provide readers with a sufficient foundation to read and evaluate empirical work and, if they so desire, to begin to design studies of their own. After attending our workshops, many participants (students and faculty alike) delved further into the subjects we covered and, ultimately, went on to produce high-quality empirical studies. We hope An Introduction to Empirical Legal Research encourages a similar investment of time with equally good results.

Let's get started.

St. Louis, Missouri, USA
Ann Arbor, Michigan, USA


1 In Chapter 1, we flesh out the meaning of "empirical work." Suffice it to note here that data in empirical studies come in two flavors: quantitative (numerical) and qualitative (non-numerical). Neither is any more "empirical" than the other (see Epstein and King, 2002).

2 Though certainly not as long as in the sciences. Stigler (1986, 2) puzzles over why "it is only in the twentieth century that [statistical methods made] substantial inroads into the social sciences. Were nineteenth-century social scientists unable to read?"

3 For documentation of the increasing use of data in law reviews and journals, see George (2005). She contends that "Empirical legal scholarship is arguably that next big thing in legal intellectual thought" (p. 141). But she also notes that "empirical research in law is not new" (see also Kritzer, 2009; Schlegel, 1995).

This is certainly true in the United States where several early empirical studies have attained landmark status, including Clark and Shulman (1937); Frankfurter and Landis (1928); Kalven and Zeisel (1966); Landes and Posner (1976). Though data work was slower to catch on in other corners of the world, no longer is "a lively interest in empirical legal research...confined to the United States and the UK;" there are "active communities of empirical legal researchers" in Australia, Canada, the Netherlands, Belgium, Spain, Germany, Israel, and Japan (Cane and Kritzer, 2010, 2). The World Bank notably supports empirical work in many new democracies with the goal of increasing their economic prosperity by improving their legal systems.

4 For well-known examples, see Erickson and Simon (1998); Loh (1984); Monahan and Walker (2010).

5 Holmes (1897, 469). Our emphasis.

6 Justice Stephen G. Breyer of the U.S. Supreme Court (2000, 2) put it this way (our emphasis):

The legal disputes before us increasingly involve the principles and tools of science. Proper resolution of those disputes matters not just to the litigants, but also to the general public—those who live in our technologically complex society and whom the law must serve. Our decisions should reflect a proper scientific and technical understanding so that the law can respond to the needs of the public. …[W]e judges [are] not asked to become expert statisticians, but we [are] expected to understand how the statistical analyses worked.

7 To be sure, there are scores of excellent texts aimed at training budding social scientists in research methods and statistics. On research design/methods, see Babbie (2009); Johnson et al. (2007a); King et al. (1994). General statistics texts include Agresti and Finlay (2009); DeGroot and Schervish (2012); Freedman et al. (2007).

It is also true that the principles are the same from book to book—a linear regression is a linear regression regardless of whether it appears in a text written for economists, sociologists, political scientists, or legal academics. It is the way the principles are conveyed and the examples invoked that can differ markedly. Within the law world, there tend to be two types of books on empirical research. The first focuses exclusively (or nearly so) on probability and statistics (e.g., Finkelstein, 2009; Finkelstein and Levin, 2001; Good, 2001; Jackson et al., 2011). They do an excellent job covering the basics (e.g., descriptive statistics) and even more advanced topics (e.g., the assumptions of regression models). But most do not mention, much less detail, topics central to understanding and evaluating empirical legal research, including research design, measurement, and data presentation. We could say the same of several reference guides prepared specifically for lawyers and judges, including Kaye and Freedman (2000).

The second type explores how courts use social science evidence. Prominent examples include Erickson and Simon (1998); Loh (1984); Monahan and Walker (2010). These too are excellent books but they are not meant to teach members of the legal community how to conduct empirical research (though they are valuable guides to how U.S. courts treat statistical studies). This leaves Lawless, Robbennolt, and Ulen's Empirical Methods in Law (2010), which is primarily a text for law students.

8 See, e.g., Epstein and King (2002); Epstein and Martin (2005, 2010); Epstein et al.(2007, 2006); Martin (2008).

9 If we were teaching this book at a workshop, we might say that only by entering the sausage factory will you understand how sausages are made—though we hope to make the process of learning about how experts produce their studies more pleasant than observing the production of sausages.





Andrew D. Martin
Lee Epstein

Lee Epstein is the Ethan A.H. Shepley Distinguished University Professor at Washington University in St. Louis. Andrew D. Martin is Dean of the College of Literature, Science, and the Arts and Professor of Political Science at the University of Michigan. For 13 years, they have taught "Conducting Empirical Legal Scholarship"—an annual workshop for law school professors, political science faculty, and graduate students interested in learning about empirical research and how to evaluate empirical work.

The Workshop

The 15th annual workshop on Conducting Empirical Legal Scholarship, co-taught by Lee Epstein and Andrew D. Martin, will run from June 15-June 17 at Washington University in St. Louis. The workshop is for law school faculty, lawyers, political science faculty, and graduate students interested in learning about empirical research and how to evaluate empirical work. It provides the formal training necessary to design, conduct, and assess empirical studies, and to use statistical software (Stata) to analyze and manage data.

Participants need no background or knowledge of statistics to enroll in the workshop. Registration is here. For more information, please contact Lee Epstein.