Cause and Effect in Antidiscrimination Law

Author:Hillel J. Bavli
Position:Assistant Professor of Law, SMU Dedman School of Law
Pages:483-554
483
Cause and Effect in Antidiscrimination
Law
Hillel J. Bavli*
ABSTRACT: Standards of causation in antidiscrimination law, and
disparate-treatment cases in particular, are deeply flawed. Their defects have
caused an illogical, obscure, and unworkable proof scheme that requires an
overhaul to curb the harm that it engenders and to allow the
antidiscrimination statutes to serve their objectives effectively. This Article
proposes a theory and method of causation that achieves this goal. The
problem stems from the inadequacies associated with current standards of
causation in disparate-treatment cases—the but-for test and the motivating-
factor test. The proposed “factorial” approach introduces a causal standard
that addresses these inadequacies. It entails three innovations over current
causation schemes: (1) it adopts a predominant framework for cause and
effect in the sciences, called the “potential-outcomes” framework, as a central
structure in which to sharply define and analyze the causal inquiry; (2) it
employs a causal measure, called the “NESS” test, that refines and, in a sense,
unifies the but-for and motivating-factor tests by retaining the central feature
of the but-for test—the “necessity condition”—but in a less restrictive form;
and (3) it applies a legal framework grounded in tort law and recent
advances regarding multiple sufficient causes. In addition to reflecting actual
cause and effect, the proposed approach promotes antidiscrimination law’s
deterrence and fairness objectives, and it allows an interpretation of causal
language in antidiscrimination statutes that is consistent with good policy
and Congress’s intent—an interpretation not possible under current
standards.
I.INTRODUCTION ............................................................................. 485
II. CAUSATION IN DISPARATE-TREATMENT CASES ............................. 490
A.SCRAMBLING FOR A LOGICAL CAUSAL STANDARD ...................... 490
*
Assistant Professor of Law, SMU Dedman School of Law. The author wishes to thank
Barry Goldstein, Ellen Katz, Nina Varsava, Tirthankar Dasgupta, Daniel Hemel, Edward Cheng,
Grant Hayden, Donald Rubin, and the participants of the Michigan Law School 2020 Junior
Scholars Conference for their helpful comments and analysis, and Sophie Franks and Laura
Sundin for their valuable editing and research assistance.
484 IOWA LAW REVIEW [Vol. 106:483
B.THE UNDERLYING PROBLEM: MIXED-MOTIVE CASES AS
MULTIPLE-SUFFICIENT-CAUSE SITUATIONS ............................... 494
III.A STRONGER FOUNDATION FOR THE CAUSAL INQUIRY ................. 501
A.THE IMPORTANCE OF “MAKING A DIFFERENCE ........................ 501
B.THE BUT-FOR STANDARD AS OVER-RESTRICTIVE ....................... 503
C.POTENTIAL OUTCOMES: A ROBUST CAUSAL FRAMEWORK .......... 504
1.Identifying the Building Blocks
of the Causal Inquiry ..................................................... 505
2.Replication, Experimentation, and
Covariate Balance .......................................................... 507
3.Defining a Causal Effect ............................................... 510
D.THE LOGIC OF A MAIN-EFFECTS ANALYSIS—A BROADER
FORM OF “DIFFERENCE ........................................................... 512
E.NESS: A (LIBERAL) MAIN-EFFECTS MEASURE ........................... 514
IV.A FACTORIAL FRAMEWORK FOR DISPARATE-TREATMENT
CASES ............................................................................................ 516
A.PROVING CAUSATION ............................................................... 517
B.THE CENTRALITY OF THE POTENTIAL-OUTCOMES
FRAMEWORK ........................................................................... 525
1.Thinking Precisely About Proof ................................... 525
2.Distinguishing Covariates from Intermediate
Variables ......................................................................... 526
i.Appropriate Comparisons ........................................... 527
ii.Preemptive Causation ................................................ 528
3.Developing Credible Statistical Evidence .................... 531
C.THE ROLE OF DAMAGES IN PREVENTING WINDFALL
RECOVERIES ............................................................................ 532
V.IMPLICATIONS ............................................................................... 536
A.THE DETERRENCE OBJECTIVES OF ANTIDISCRIMINATION
LAW ....................................................................................... 536
1.The Motivating-Factor Test .......................................... 538
2.But-For Causation.......................................................... 540
3.The Factorial Framework ............................................. 540
4.Effect Categories ........................................................... 542
B.CAUSAL LANGUAGE IN ANTIDISCRIMINATION STATUTES ............ 545
C.AN APPLICATION: THE SUPREME COURTS DECISIONS IN
COMCAST AND BABB .............................................................. 549
VI.CONCLUSION ................................................................................ 553
2021] CAUSE AND EFFECT IN ANTIDISCRIMINATION LAW 485
I. INTRODUCTION
Standards of causation in antidiscrimination law, and disparate-
treatment cases in particular, are deeply fla wed. Th ey can b e descr ibed, i n the
words of Dr. Seuss, as a “muddled duddled fuddled wuddled fox in socks.”1
That’s a metaphor for causation doctrine that entails not only a tangled web
of inconsistent rules and conditions but also causal standards that are not
quite right in the first instance. The problem stems from the inadequacies
associated with current standards of causation in disparate-treatment cases
—the “but-for” test and the “motivating-factor” test.
Causation is the element of a legal claim that connects a defendant’s
misconduct to a plaintiff’s injury.2 As the Supreme Court has stated, “When
the law grants persons the right to compensation for injury from wrongful
conduct, there must be some demonstrated connection, some link, between
the injury sustained and the wrong alleged. The requisite relation between
prohibited conduct and compensable injury is governed by the principles of
causation . . . .”3
The most basic and pervasive standard of causation in the law is the but-
for standard.4 It asks whether the outcome would have occurred in the
absence of the alleged conduct.5 The defendant’s conduct is a but-for cause
of the plaintiff’s harm if, in the absence of the alleged conduct, the plaintiff’s
harm would not have occurred.6 The but-for test is generally simple and
provides a straightforward method for determining actual cause and effect.7
It is based on the “necessity condition”—on whether the defendant’s conduct
“made a difference.”
In disparate-treatment cases, however, the but-for test is frequently
inadequate as a standard of causation. This is because most disparate-
treatment cases involve allegations of at least two possible factors (or “mixed
motives”) leading to an adverse employment action—one illegitimate (i.e.,
discriminatory) and one legitimate.8 This occurs for two reasons. First,
employment decisions, such as whom to hire, fire, or promote, or how much
to pay an employee, are complex, often involving multiple factors. Second, it
1. DR. SEUSS, FOX IN SOCKS 59 (1993).
2. Comcast Corp. v. Nat’l Ass’n of Afr. Am.-Owned Media, 140 S. Ct. 1009, 1013 (2020);
Univ. of Tex. Sw. Med. Ctr. v. Nassar, 570 U.S. 338, 342 (2013).
3. Nassar, 570 U.S. at 342.
4. DAN B. DOBBS, PAUL T. HAYDEN & ELLEN M. BUBLICK, HORNBOOK ON TORTS 317 (2d ed.
2016).
5. Id.
6. Id.
7. Throughout this Article, I use the terms “cause and effect” or “causal” effect to refer to
the generic causal concept, “causation” to refer to the legal causal concept, and “causality” or
“causal inference” to refer to the scientific or statistical causal concept.
8. See BARBARA T. LINDEMANN, PAUL GROSSMAN & C. GEOFFREY WEIRICH, EMPLOYMENT
DISCRIMINATION LAW 2-2–3 (5th ed. 2012).

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