interpretation of Regulation B [
18
] all support the general consen-
sus that disparate impact theory is cognizable under ECOA. Federal
courts have consistently upheld this since the 1980s [23].
Plaintis usually rely on burden-shifting systems for establishing
aprima facie claim under both theories, which can then be rebut-
ted by the defendant. For a disparate treatment case, most circuit
courts have found that a modication of the McDonnell-Douglas
test, originally developed by the Supreme Court in an employment
discrimination case [
2
], can be applied to an ECOA claim–but there
is no ocial nationwide rule on the issue [
11
]. In a prima facie
disparate impact claim [
1
], a plainti must point to a specic policy
or action taken by the defendant that had a disproportionately ad-
verse impact on members of a protected class. The defendant may
respond by arguing there is a legitimate business necessity for the
policy. Then, the plainti can respond by arguing there was a less
discriminatory alternative that the defendant refused to use.
In a disparate impact claim, expert statistical testimony is neces-
sary to demonstrate that an adverse impact exists and is dispropor-
tionately felt by members of a protected class [
11
]. Again, we lack
ocial Supreme Court guidance on how exactly to go about this
under ECOA. In employment discrimination cases, however, the
ratio of the proportion of protected class that receives a favorable
outcome and the proportion of the control class is used; the oft-
cited "80% rule" is related to this statistic [
29
]. A related metric with
precedence in the credit setting is the standardized mean dierence
of outcomes for two groups [
44
]. However, it is usually insucient
to simply compare the approval rates of two groups of applicants;
since information related to creditworthiness is generally available,
higher courts generally expect that plaintis will compare the se-
lection rates of qualied applicants [
11
]. For this reason, statistical
evidence which controls for drivers of creditworthiness–such as a
conditional marginal eects test–are seen as more appropriate by
federal agencies [19].
It is dicult for plaintis to nd evidence that an individual lend-
ing decision was discriminatory, especially in the non-mortgage
setting where sensitive attribute data about applicants is generally
unavailable; some lower courts have historically acknowledged this
[
84
]. Bogen et al
. [14]
point out that "one of the few, robust public
studies on credit scores and discrimination in the United States
was performed by the FRB in 2007, at the direction of Congress.
To conduct its analysis, the FRB created a database that, for the
rst time, combined sensitive attribute data collected by the Social
Security Administration with a large, nationally representative sam-
ple of individuals’ credit records... this unusual undertaking would
not have been possible without signicant governmental time and
resources." Interestingly, the CFPB has worked around this data
limitation in some of its enforcement actions by imputing racial
information using Bayesian Improved Surname Geocoding (BISG)
to amass evidence of disparate impact [
6
]. On the other hand, in the
mortgage setting where data is available, HMDA data alone cannot
prove or disprove discrimination, and the results of discrimination
studies using HMDA data are usually contentious [75].
An important precedent is, of course, the general acceptance of
traditional credit scores as a basis of loan underwriting. Like the ma-
chine learning algorithms which are the focus of this paper, credit
scores are functions of data which are meant to provide a quantita-
tive basis on which to make a lending decision. As of yet, there have
not been successful challenges against credit scores using disparate
impact theory [
51
]. A combination of factors has contributed to this,
but one seems to be that ocial CFPB interpretations of ECOA and
OCC guidance on models are fairly generous as to what counts as
a business necessity and relation to creditworthiness, respectively
[
11
]. Further complicating this matter is the fact that creditors tend
to (credibly) argue that their scoring methods tend to expand credit
to minority applicants when compared to other methods. The FRB
bolstered the credit score’s ubiquity in their analysis of the 2007
database: they claimed that while credit scores have a “dierential
eect" [
70
], they did not "produce a disparate impact" [
7
] because
credit characteristics do not act as "proxies for race and ethnic-
ity" according to their own denition (which we will discuss the
limitations of in Section 2).
1.3 Agency communications on fair lending in
algorithms
In this section, we analyze recent messaging from several federal
agencies on the threat of algorithmic fairness in nance and credit.
These agencies are generally allowed to operate independently, but
many have been known to act cooperatively and take a unied
stance on the interpretation of the law [
77
]. The OCC, FRB, FDIC,
and CFPB recently issued a rare joint request for information re-
garding the use of articial intelligence (AI) in nancial services,
inquiring, among other things, whether banks and other interested
parties feel that additional regulatory guidance on the matter is
necessary [
74
]. Their response to the threat of algorithmic discrim-
ination will be highly inuential since, as Alex Engler has argued,
"major legislative changes to AI oversight seem unlikely in the near
future, which means that regulatory interventions will set prece-
dent for the government’s approach to protecting citizens from AI
harms" [36].
1.3.1 The Consumer Financial Protection Bureau (CFPB). The CFPB
was created by the Dodd-Frank Wall Street Reform and Consumer
Protection Act in 2011. It was designed to consolidate responsibili-
ties from several other agencies such as the Federal Reserve, FTC,
and FDIC, to write and enforce rules for both bank and non-bank
nancial institutions. It has situated itself as being well-posed to
tackle new regulatory challenges introduced by technology. The
CFPB’s internal “Oce of Competition and Innovation," dedicated
in part to addressing these challenges, has taken initiatives such as
holding tech sprints, issuing no-action letters (NALs), and develop-
ing compliance assistance sandboxes.
The most relevant action the CFPB has taken with respect to
algorithmic discrimination was its NAL to ntech lending company
Upstart in 2017. Upstart provided detailed public (and some private)
information about its underwriting process with the bureau and
requested a formal statement from the CFPB that they would not
trigger any enforcement action [
86
]. The CFPB granted the NAL.
Part of the terms of the letter stipulated that Upstart would send
the CFPB updates "regarding the loan applications it receives, how
it decides which loans to approve, and how it will mitigate risk to
consumers, as well as information on how its model expands access
to credit for traditionally underserved populations" to "further its
understanding of how these types of practices impact access to
credit generally and for traditionally underserved populations, as