Court Opinion

ID: 9962044
Source: CourtListenerOpinion
Date Created: 2024-04-22 16:02:08.464073+00
Date Added: 2024-06-11T08:19:42.269097
License: Public Domain

FOR PUBLICATION

    UNITED STATES COURT OF APPEALS
         FOR THE NINTH CIRCUIT

JUSTIN LYTLE and CHRISTINE                     No. 22-55744
MUSTHALER,
                                                  D.C. No.
                Plaintiffs-Appellees,          5:19-cv-00835-
    v.                                            FMO-SP

NUTRAMAX LABORATORIES,
INC. AND NUTRAMAX                                OPINION
LABORATORIES VETERINARY
SCIENCES, INC,

                Defendants-Appellants.

          Appeal from the United States District Court
              for the Central District of California
         Fernando M. Olguin, District Judge, Presiding

           Argued and Submitted October 18, 2023
                    Pasadena, California

                     Filed April 22, 2024

Before: A. Wallace Tashima and Holly A. Thomas, Circuit
        Judges, and Jed S. Rakoff, * District Judge.

*
 The Honorable Jed S. Rakoff, United States District Judge for the
Southern District of New York, sitting by designation.
2             LYTLE V. NUTRAMAX LABORATORIES, INC.

                    Opinion by Judge Rakoff

                          SUMMARY **

                           Class Action

    The panel affirmed the district court’s grant of class
certification in a consumer class action concerning the
marketing of the pet health product Cosequin.
    Plaintiffs claim that Nutramax violated the California
Consumers Legal Remedies Act (“CLRA”) by marketing
Cosequin as promoting healthy joints in dogs, when in fact
Cosequin provides no such health benefit. The district court
certified a class of California purchasers of certain Cosequin
products who were exposed to the allegedly misleading
statements.
    Nutramax challenged the district court’s reliance upon
the proposed damages model of Plaintiffs’ expert, Dr. Jean-
Pierre Dubé, to find that common questions predominated as
to injury. The panel held that, contrary to Nutramax’s
contention, there was no general requirement that an expert
actually apply to the proposed class an otherwise reliable
damages model in order to demonstrate that damages are
susceptible to common proof at the class certification
stage. Rather, class certification plaintiffs may rely on an
unexecuted damages model to show that damages are
susceptible to common proof. The panel concluded that the

**
  This summary constitutes no part of the opinion of the court. It has
been prepared by court staff for the convenience of the reader.
            LYTLE V. NUTRAMAX LABORATORIES, INC.           3

district court did not abuse its discretion in finding that
Dr. Dubé’s proposed model was sufficiently sound and
developed to satisfy this standard at the class certification
stage.
    The panel rejected Nutramax’s contention that the
district court incorrectly concluded that the element of
reliance was susceptible to common proof. The district court
properly found that classwide reliance may be established
under the CLRA through proof that a misrepresentation is
material. While the presumption of reliance is rebuttable,
the district court did not abuse its discretion in concluding
that Nutramax failed to rebut the presumption here.

                        COUNSEL

David R. Carpenter (argued), Sean A. Commons, Nicole M.
Baade, and Amy P. Lally, Sidley Austin LLP, Los Angeles,
California; Joshua A. Glikin, Bowie & Jensen LLC,
Townson, Maryland; for Defendants-Appellants.
Mark R. Sigmon (argued), Milberg Coleman Bryson Phillips
Grossman PLLC, Raleigh, North Carolina; Greg F. Coleman
and Adam A. Edwards, Milberg Coleman Bryson Phillips
Grossman PLLC, Knoxville, Tennessee; Michael H. Pearson
and Daniel L. Warshaw, Pearson Simon & Warshaw LLP,
Sherman Oaks, California; Matthew D. Schultz, Levin
Papantonio Rafferty Proctor Buchanan O’Brien Barr &
Mougey PA, Pensacola, Florida; for Plaintiffs-Appellees.
4            LYTLE V. NUTRAMAX LABORATORIES, INC.

                          OPINION

RAKOFF, District Judge:

    This is a putative consumer class action concerning the
marketing of the pet health product Cosequin. Plaintiffs-
Appellees claim that Nutramax Laboratories, Inc. and
Nutramax Laboratories Veterinary Sciences, Inc.
(collectively, “Nutramax”) violated the California
Consumers Legal Remedies Act (“CLRA”), Cal. Civil Code
§§ 1750–1784, by marketing Cosequin as promoting healthy
joints in dogs, when in fact Cosequin provided no such
health benefits. Below, the district court certified a class of
California purchasers of certain Cosequin products who
were exposed to the allegedly misleading statements.
Nutramax now appeals that grant of class certification on
two grounds.
    First, Nutramax challenges the district court’s reliance
upon the proposed damages model of Plaintiffs’ expert,
Dr. Jean-Pierre Dubé, to find that common questions
predominated as to injury. Nutramax claims this was error
because the proposed model had not actually been applied to
the proposed class. We conclude that, contrary to
Nutramax’s contention, there is no general requirement that
an expert actually apply to the proposed class an otherwise
reliable damages model in order to demonstrate that
damages are susceptible to common proof at the class
certification stage. Rather, we hold that class action plaintiffs
may rely on a reliable though not-yet-executed damages
model to demonstrate that damages are susceptible to
common proof so long as the district court finds that the
model is reliable and, if applied to the proposed class, will
be able to calculate damages in a manner common to the
            LYTLE V. NUTRAMAX LABORATORIES, INC.             5

class at trial. We further conclude that the district court did
not abuse its discretion in finding Dr. Dubé’s proposed
model was sufficiently sound and developed to satisfy this
standard at the class certification stage.
    Second, Nutramax contends that the district court
incorrectly concluded that the element of reliance was
susceptible to common proof. We disagree. The district court
properly found that classwide reliance may be established
under the CLRA through proof that a misrepresentation is
material. While the presumption of reliance is rebuttable, the
district court did not abuse its discretion in concluding
Nutramax had failed to rebut the presumption here.
   Accordingly, for the reasons set forth more fully below,
we affirm the district court’s grant of class certification.
                              I.
    Nutramax develops and sells pet health supplements.
Plaintiffs-Appellees Justin Lytle and Christine Musthaler are
two dog owners who purchased a product produced by
Nutramax, Cosequin, for their dogs. In this action, Plaintiffs
allege that Nutramax marketed Cosequin as a health
supplement that would improve their dogs’ joints and
mobility when, in fact, there is no evidence that Cosequin
provides any such health benefit.
    After the close of fact and expert discovery, Plaintiffs
sought to certify the following class pursuant to Federal Rule
of Civil Procedure (“FRCP”) 23(b)(3):

       All persons residing in California who
       purchased during the limitations period the
       following canine Cosequin products for
       personal use: Cosequin DS Maximum
6           LYTLE V. NUTRAMAX LABORATORIES, INC.

       Strength Chewable Tablets; Cosequin DS
       Maximum Strength Plus MSM Chewable
       Tablets; and Cosequin DS Maximum
       Strength Plus MSM Soft Chews.

    Plaintiffs initially asserted that numerous statements
made in marketing materials for Cosequin and/or on the
packaging of the three products listed above were false and
misleading. However, at class certification Plaintiffs
narrowed their claims to four statements that appeared on
Cosequin’s packaging:

       (1): “Joint Health Supplement”;
       (2): “Use Cosequin to help your pet Climb
             stairs, Rise and Jump!”;
       (3): “Supports Mobility       for   a   Healthy
             Lifestyle”; and
       (4): “Mobility, Cartilage and Joint Health
             Support.”

    Plaintiffs argued that these statements were false and
misleading because Cosequin does not, in fact, improve
dogs’ joint health. According to Plaintiffs, the only two peer-
reviewed, double-blinded, randomized controlled trials that
have been conducted on Cosequin’s efficacy have concluded
that Cosequin confers no more benefit to canine joint health
than a placebo. Plaintiffs’ veterinary expert Dr. Steven
Budsberg opined that “the strongest available
evidence . . . has consistently found no reliable evidence that
Cosequin provides any efficacy in supporting, maintaining,
or improving joint health,” and Plaintiffs’ biostatistics expert
Dr. Richard Evans concluded that “there is no evidence that
[glucosamine and chondroitin, the active ingredients in
            LYTLE V. NUTRAMAX LABORATORIES, INC.           7

Cosequin, have] a greater prophylactic effect than placebo
control on maintaining joint health in healthy pet dogs.”
Nutramax, for its part, presented contrary evidence about the
products’ efficacy, including non-randomized control trials
and the testimony of Nutramax’s own veterinary expert,
Dr. Marcellin-Little. Nutramax further argues that the two
studies relied on by Plaintiffs involved dogs with
osteoarthritis, even though Cosequin is not marketed to treat
that condition. The district court found that Plaintiffs had
adequately demonstrated for class certification purposes the
reasonable likelihood that a jury could find that Cosequin
provided no benefit to dogs’ joint health.
    The four challenged statements appeared on the labels of
various Cosequin products in various combinations over
time. Although the parties offer differing characterizations
about the extent and significance of these variations, the
parties agree that the first statement (“Joint Health
Supplement”) appeared on all product labels or packages
throughout the class period. Further, approximately 90% of
sales during the class period—including those to the named
plaintiffs—were attributable to products that contained the
“Joint Health Supplement” statement. The district court
ultimately found that the presence of the Joint Health
Supplement statement on every challenged product was
sufficient to support class certification.
    Before the district court, Nutramax raised a host of
challenges to Plaintiffs’ class certification motion,
contesting each prerequisite of FRCP 23(a) and 23(b)(3).
Nutramax also belatedly filed two evidentiary objections to
Plaintiffs’ expert witnesses Bruce Silverman and Dr. Dubé .
The district court rejected each of these objections and
certified the class as requested by Plaintiffs. Nutramax then
promptly sought and obtained permission to file the instant
8           LYTLE V. NUTRAMAX LABORATORIES, INC.

interlocutory appeal of the district court’s class certification
order pursuant to FRCP 23(f).
     On appeal, Nutramax limits its challenge to just two of
the district court’s findings: (1) that damages are susceptible
to common proof, and (2) that causation/reliance is
susceptible to common proof. Nutramax also persists in its
evidentiary objection to Dr. Dubé insofar as it relates to the
first question of whether damages are susceptible to common
proof. The parties’ briefing and the district court’s rulings on
these two issues are briefly described below.
                              A.
     To establish damages on a classwide basis, Plaintiffs put
forward the testimony of Dr. Dubé, a professor of marketing
at the University of Chicago Booth School of Business who,
as the district court found, has “extensive experience in
marketing data and analytics.” To measure classwide
damages, Dr. Dubé proposed to conduct a “conjoint survey”
(or “conjoint analysis”). Simply put, a conjoint survey
allows a researcher to test the economic value a consumer
places on a given product feature, such as a particular
statement on a package, by showing the product to individual
survey participants with and without certain features, and
then using survey responses to calculate the economic value
consumers place upon the feature. Dr. Dubé explained that,
in conducting a conjoint analysis, a researcher is able to
control for other variables such as package size and the
competing products by modifying the underlying choice-
tasks presented to participants.
    At the time of class certification, Dr. Dubé had not yet
actually applied his conjoint analysis to a representative
sample in the case, that is, he had not actually surveyed any
class members or calculated what class members’ damages
             LYTLE V. NUTRAMAX LABORATORIES, INC.              9

might be. Rather, in his report, Dr. Dubé opined that,
“[b]ased on [his] analysis of market data and other marketing
documents made available through discovery,” he believed
a conjoint analysis “is well-suited to the facts of this case and
will successfully isolate the economic damages associated
with the Challenged Claims.” Dr. Dubé acknowledged,
however, that he would not know whether the class actually
suffered any damages until he actually executed his survey.
    Nutramax’s class certification opposition criticized
Dr. Dubé for failing to actually conduct (i.e., “execute”) the
survey and thus complete his analysis. Before the district
court, Nutramax also argued that Dr. Dubé’s model was
under-developed in other respects, although Nutramax
apparently did not argue this was a basis to exclude his
testimony under Federal Rule of Evidence (“FRE”) 702 or
FRCP 23, but instead argued that his opinion violated FRCP
16, 26, 37 and the district court’s scheduling order.
    The district court rejected Nutramax’s argument that it
could not rely on Dr. Dubé’s unexecuted damages model or
that the model should be excluded under the standard set
forth in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509
U.S. 579 (1993). The district court began by noting
Dr. Dubé’s credentials, finding him to be well qualified for
the purposes offered. The district court further observed that
conjoint surveys such as that proposed by Dr. Dubé “are a
well-established method for measuring class-wide damages
in CLRA mislabeling cases,” and also noted that conjoint
analyses previously prepared by Dr. Dubé had been upheld
as reliable in similar cases. Most importantly, the court
below, citing other district court precedent, held that “[a]
plaintiff is not required to actually execute a proposed
conjoint analysis to show that damages are capable of
determination on a class-wide basis.”
10            LYTLE V. NUTRAMAX LABORATORIES, INC.

                                  B.
    Nutramax also opposed class certification on the ground
that individual questions predominated with respect to the
element of reliance because (1) substantial variation in the
labels precluded a finding of predominance, (2) Plaintiffs
had failed to show common exposure to the challenged
statements, and (3) Plaintiffs had not shown the challenged
statements factored into the typical consumer’s purchasing
decision or would have been material to such consumers.
Although reliance and materiality are separate elements,
under the CLRA, a plaintiff can create a presumption of
reliance by demonstrating a material misrepresentation was
made to the entire class. See Stearns v. Ticketmaster Corp.,
655 F.3d 1013, 1022 (9th Cir. 2011). To establish materiality
(and relatedly, reliance for class certification purposes),
Plaintiffs put forward the expert testimony of Silverman, a
former advertising executive, who testified that a reasonable
consumer would find the product labels misleading. As
noted, Plaintiffs also put forward two expert witnesses,
Dr. Budsberg and Dr. Evans, to testify to the falsity of the
challenged statements and demonstrate that Cosequin did
not offer joint health benefits. Plaintiffs also argued that the
survey conducted by Nutramax’s own expert, Dr. Carol
Scott, actually supported a finding of materiality. 1

1
  In this regard, Plaintiffs homed in on one particular finding of
Dr. Scott’s survey that they claimed actually supports a finding of
materiality. Dr. Scott showed respondents a label from Product #2,
containing only the Joint Health Supplement statement, and asked:
“Based on this package, what do you think[] Cosequin will do for your
dog? That is, why should you give your dog Cosequin?” The “most
frequently given response” (by nearly 80% of respondents) was
“improve/help/maintain mobility, flexibility, joint health/support.” In
              LYTLE V. NUTRAMAX LABORATORIES, INC.                   11

    In response, Nutramax put forward two experts. First,
Nutramax put forward Dr. Scott to present the results of a
consumer survey about the purchasing decisions of
Cosequin customers. Dr. Scott’s survey found that
purchasers “consulted a variety of information sources prior
to purchasing [Cosequin] for the first time, with one’s
veterinarian being most frequently mentioned (i.e., 57% of
respondents . . . ), followed by website ratings or reviews
(26.9% of respondents).” Only about a quarter of
respondents identified the packaging as a source of
information they consulted prior to deciding to purchase
Cosequin for the first-time. Dr. Scott’s survey found that the
most common motivations for purchasing Cosequin were
advice from a veterinarian, advice from someone else, or
research on websites, whereas only a small fraction of
respondents cited the packaging for their motive. Second,
Nutramax put forward Dr. Olivier Toubia, who conducted a
consumer choice survey somewhat similar to that proposed
by Dr. Dubé. Dr. Toubia showed one group of individuals
the actual product packaging and another group a modified
version that (supposedly) removed the challenged claims.
The results of this study, according to Dr. Toubia, showed
that removing the statements did not materially impact the
price a consumer would be willing to pay.
    The district court reviewed the evidence presented by the
parties and ultimately credited the evidence presented by
Plaintiffs that the challenged statements would be materially
misleading to a reasonable consumer. In a footnote, the
district court explained that it was “unpersuaded” by

the district court and on appeal, Plaintiffs argue that this finding by
Dr. Scott further demonstrates that the challenged statements would have
been misleading to a reasonable consumer.
12           LYTLE V. NUTRAMAX LABORATORIES, INC.

Dr. Scott’s and Dr. Toubia’s expert reports, noting that they
contained “flaws that undercut their persuasiveness.” In
particular, the district court cited the fact that Dr. Toubia’s
survey failed to remove the “Joint Health Supplement”
statement from the packaging, even though that was at the
core of Plaintiffs’ claim. The district court did not explain
the basis for its rejection of Dr. Scott’s survey, but ultimately
concluded Nutramax’s evidence was “outweighed by the
common evidence presented by plaintiffs.”
                              II.
    Before a class may be certified, the district court must
conduct a “rigorous analysis” to determine if the
prerequisites of FRCP 23 have been satisfied. Olean
Wholesale Grocery Coop., Inc. v. Bumble Bee Foods LLC,
31 F.4th 651, 664 (9th Cir. 2022) (en banc). The plaintiffs
must “actually prove—not simply plead—that their
proposed class satisfies each requirement of Rule 23.”
Halliburton Co. v. Erica P. John Fund, Inc., 573 U.S. 258,
275 (2014). The plaintiffs bear “the burden of establishing
that the prerequisites of Rule 23 are satisfied by a
preponderance of the evidence.” Olean, 31 F.4th at 665.
    At issue here is the predominance requirement: that
“questions of law or fact common to class members
predominate over any questions affecting only individual
members.” FRCP 23(b)(3). This requirement presupposes
satisfaction of the commonality requirement of FRCP
23(a)(2), which itself tests “the capacity of a classwide
proceeding to generate common answers apt to drive the
resolution of the litigation.” Alcantar v. Hobart Serv., 800
F.3d 1047, 1052 (9th Cir. 2015) (quoting Wal-Mart Stores,
Inc. v. Dukes, 564 U.S. 338, 350 (2011)). But the
predominance inquiry goes further and “asks whether the
            LYTLE V. NUTRAMAX LABORATORIES, INC.            13

common, aggregation-enabling, issues in the case are more
prevalent or important than the non-common, aggregation-
defeating, individual issues.” Tyson Foods, Inc. v.
Bouaphakeo, 577 U.S. 442, 453 (2016).
    At the same time, it is critical to keep in mind that class
certification is different from summary judgment. “A
court . . . is merely to decide [whether a class action is] a
suitable method of adjudicating the case.” Edwards v. First
Am. Corp., 798 F.3d 1172, 1178 (9th Cir. 2015). With
respect to the predominance inquiry specifically, a district
court must evaluate “‘the method or methods by which
plaintiffs propose to use the [class-wide] evidence to prove’
the common question in one stroke.” Olean, 31 F.4th at 666
(quoting In re Hydrogen Peroxide Antitrust Litig., 552 F.3d
305, 312 (3d Cir. 2008)). “In determining whether the
‘common question’ prerequisite is met, a district court is
limited to resolving whether the evidence establishes that a
common question is capable of class-wide resolution, not
whether the evidence in fact establishes that plaintiffs would
win at trial.” Olean, 31 F.4th at 666–67.
    We review the “decision to certify a class and any
particular underlying Rule 23 determination involving a
discretionary determination” for an abuse of discretion.
Olean, 31 F.4th at 663 (cleaned up). We review de novo “the
district court’s determination of underlying legal questions.”
Id. “A district court applying the correct legal standard
abuses its discretion only if it (1) relies on an improper
factor, (2) omits a substantial factor, or (3) commits a clear
error of judgment in weighing the correct mix of factors.”
Sali v. Corona Reg’l Med. Ctr., 909 F.3d 996, 1004 (9th Cir.
2018) (cleaned up). We review evidentiary rulings for an
abuse of discretion. City of Pomona v. SQM N. Am. Corp.,
750 F.3d 1036, 1043 (9th Cir. 2014). We review factual
14            LYTLE V. NUTRAMAX LABORATORIES, INC.

findings underlying a class certification ruling for clear
error. Sali, 909 F.3d at 1002. We review the question of
whether an expert’s damages model “is capable of showing
class-wide impact, thus satisfying one of the prerequisites of
Rule 23(b)(3) of the Federal Rules of Civil Procedure, for an
abuse of discretion.” Olean, 31 F.4th at 663. Finally, we
“give the district court ‘noticeably more deference when
reviewing a grant of class certification than when reviewing
a denial.’” Patel v. Facebook, Inc., 932 F.3d 1264, 1275 (9th
Cir. 2019) (quoting Just Film, Inc. v. Buono, 847 F.3d 1108,
1115 (9th Cir. 2017)).
                                  III.
                                   A.
     Nutramax’s principal argument on appeal is that the
“rigorous analysis” required by FRCP 23 categorically
prohibits a class-action plaintiff from relying on an
unexecuted damages model to demonstrate predominance
(at least where that model is the only evidence of classwide
injury). 2 In addressing this argument, the parties focus on the
statement in the Supreme Court’s decision in Comcast Corp.
v. Behrend—repeated in our en banc decision in Olean
Wholesale Grocery Cooperative, Inc. v. Bumble Bee Foods
LLC—that a class action plaintiff must “establish[] that
damages are capable of measurement on a classwide basis.”

2
  On appeal, the parties both appear to assume that the predominance
requirement would be satisfied only if damages are capable of
measurement on a classwide basis. For purposes of this appeal, we adopt
this assumption. We note, however, that we have held that individual
questions of damages do not necessarily defeat class certification, as the
district court here expressly acknowledged. See Vaquero v. Ashley
Furniture Indus., Inc., 824 F.3d 1150, 1155 (9th Cir. 2016); Pulaski &
Middleman, LLC v. Google, Inc., 802 F.3d 979, 987 (9th Cir. 2015).
             LYTLE V. NUTRAMAX LABORATORIES, INC.             15

569 U.S. 27, 34 (2013) (emphasis added). Plaintiffs contend
that this phrase sanctions precisely what Dr. Dubé has done
here: submit an expert report opining that damages can be
measured on a classwide basis and setting forth a reliable
method for doing so. Nutramax, by contrast, argues that to
satisfy the predominance requirement, “[P]laintiffs must
proffer admissible, affirmative evidence that classwide
injury and damages in fact are capable of classwide
measurement.” In Nutramax’s view, the only way to carry
this burden is to actually put forward common evidence
showing that classwide damages exist.
    Nutramax’s argument rests upon a misapprehension of
the temporal focus of the class certification inquiry. As
explained below, class action plaintiffs are not required to
actually prove their case through common proof at the class
certification stage. Rather, plaintiffs must show that they will
be able to prove their case through common proof at trial.
Given, moreover, that the Federal Rules contemplate that
certification will be made “[a]t an early practicable time,”
FRCP 23(c)(1)(A), we see no reason why plaintiffs may not,
in appropriate circumstances, satisfy this burden through a
proffer of a reliable method of obtaining evidence that will
come into existence once a damages model is executed, even
when the results are not yet available at the class certification
stage. We thus hold that class action plaintiffs may rely on
an unexecuted damages model to demonstrate that damages
are susceptible to common proof so long as the district court
finds, by a preponderance of the evidence, that the model
will be able to reliably calculate damages in a manner
common to the class at trial.
   Contrary to Nutramax’s contention, there is no
requirement that the evidence relied upon by Plaintiffs to
support class certification be presented in an admissible form
16             LYTLE V. NUTRAMAX LABORATORIES, INC.

at the class certification stage. See Sali, 909 F.3d at 1004
(“Inadmissibility alone is not a proper basis to reject
evidence submitted in support of class certification.”); B.K.
v. Snyder, 922 F.3d 957, 974 (9th Cir. 2019) (“At this
‘tentative, preliminary, and limited’ stage we have held
strictly admissible evidence is not required, and we have
indicated that plaintiffs can meet their evidentiary burden in
part through allegations when the allegations are detailed
and supported by additional materials” (internal citation
omitted)). As we explained in Sali v. Corona Regional
Medical Center, “an inquiry into the evidence’s ultimate
admissibility should go to the weight that evidence is given
at the class certification stage.” 909 F.3d at 1006. 3 Of course,
if it is unlikely that a particular piece of common proof will
be available or admissible at trial, that possibility weighs
against a finding that common questions (and common
answers) will predominate. But “[n]either the possibility that
a plaintiff will be unable to prove his allegations, nor the
possibility that the later course of the suit might
unforeseeably prove the original decision to certify the class
wrong, is a basis for declining to certify a class which
apparently satisfies” Rule 23. Id. at 1004–05 (quoting
Blackie v. Barrack, 524 F.2d 891, 901 (9th Cir. 1975)).
    Nor is there a requirement that class action plaintiffs
actually prove that classwide damages exist in order to
obtain class certification. Rather, we have repeatedly found
class treatment to be appropriate, in analogous contexts,
based upon a showing that damages could be calculated on

3
  The district court correctly cited Sali for this exact principle. Nutramax
inexplicably asserts the district court committed legal error by doing so
without ever discussing Sali or explaining why, in Nutramax’s view, the
rule announced in that case is inapplicable.
            LYTLE V. NUTRAMAX LABORATORIES, INC.            17

a classwide basis, even where such calculations have not yet
been performed. See Just Film, 847 F.3d at 1121 (“At this
stage, Plaintiffs need only show that such damages can be
determined without excessive difficulty and attributed to
their theory of liability, and have proposed as much here.”);
Lambert v. Nutraceutical Corp., 870 F.3d 1170, 1182 (9th
Cir. 2017) (“Uncertainty regarding class members’ damages
does not prevent certification of a class as long as a valid
method has been proposed for calculating those damages.”),
rev’d and remanded on other grounds, 139 S. Ct. 710
(2019); Leyva v. Medline Indus. Inc., 716 F.3d 510, 514 (9th
Cir. 2013) (finding evidence “that damages could feasibly
and efficiently be calculated once the common liability
questions are adjudicated” was sufficient to satisfy
predominance). For example, in Lambert v. Nutraceutical
Corp., we reversed a district court’s denial of class
certification and concluded the plaintiffs had satisfied the
predominance requirement by proposing a valid damages
model, even where the plaintiffs did not yet have all of the
data necessary to perform their damages calculations. 870
F.3d at 1183–84. We explained that the “precise [data] is
unnecessary for class certification” because “the question is
only whether [plaintiff] has presented a workable method.”
Id. at 1184.
     Requiring that class action plaintiffs actually prove
classwide injury at this stage would improperly conflate the
class certification inquiry with the merits. To be sure, courts
may not avoid resolving questions pertinent to class
certification merely because they overlap with the merits of
the plaintiffs’ case, see Wal-Mart, 564 U.S. at 351; Comcast,
569 U.S. at 33–34, but this does not “grant[]
courts . . . license to engage in free-ranging merits inquiries
at the certification stage.” Amgen Inc. v. Conn. Ret. Plans &
18           LYTLE V. NUTRAMAX LABORATORIES, INC.

Tr. Funds, 568 U.S. 455, 466 (2013). Rather, such “[m]erits
questions may be considered to the extent—but only to the
extent—that they are relevant to determining whether the
Rule 23 prerequisites for class certification are satisfied.” Id.
    While acknowledging this rule, Nutramax argues that the
theoretical possibility Dr. Dubé’s model, once executed,
might show no injury at all “goes to the heart of the Rule 23
inquiry.” But Nutramax fails to convincingly explain why
this is so. The focus of the predominance inquiry “is whether
the method of proof would apply in common to all class
members,” “not whether the method of proof would or could
prevail.” In re Celexa & Lexapro Mktg. & Sales Pracs.
Litig., 915 F.3d 1, 12 (1st Cir. 2019); see Stockwell v. City &
Cnty. of San Francisco, 749 F.3d 1107, 1112 (9th Cir. 2014)
(“[W]hether class members could actually prevail on the
merits of their claims is not a proper inquiry in determining
the preliminary question whether common questions exist.”
(internal quotation marks omitted)). As the Supreme Court
explained in Tyson Foods, Inc. v. Bouaphakeo,
“[w]hen . . . ‘the concern about the proposed class is not that
it exhibits some fatal dissimilarity but, rather, a fatal
similarity—[an alleged] failure of proof as to an element of
the plaintiffs’ cause of action—courts should engage that
question as a matter of summary judgment, not class
certification.’” 577 U.S. at 457 (quoting Richard A.
Nagareda, Class Certification in the Age of Aggregate Proof,
84 N.Y.U. L. Rev. 97, 107 (2009)); see also Amgen, 568 U.S.
at 468 (“A failure of proof on the common question of
materiality ends the litigation and thus will never cause
individual questions of reliance or anything else to
overwhelm questions common to the class.”); Alcantar, 800
F.3d at 1053 (“A common contention need not be one that
‘will be answered, on the merits, in favor of the class.’”
              LYTLE V. NUTRAMAX LABORATORIES, INC.                    19

(quoting Amgen, 568 U.S. at 459)). “To hold otherwise
would turn class certification into a mini-trial, when the
purpose of class certification is merely to select the method
best suited to adjudication of the controversy fairly and
efficiently.” Alcantar, 800 F.3d at 1053 (cleaned up).
     The theoretical possibility that Dr. Dubé’s model, when
executed, will reveal no damages thus does not undermine
predominance, because that result would nonetheless be
common to the class. 4 Nor does the possibility Dr. Dubé’s
analysis might reveal damages with respect to some, but not
all, of the challenged statements undermine predominance,
because the very structure of the conjoint survey allows for
an overcharge to be associated with each individual
statement and label, allowing the amount each class member
is entitled to recover to be easily assessed based solely on the
product the class member purchased. And the possibility that
an ascertainable portion of the class may be unable to
recover—those not exposed to a statement with any
attributable overcharge—does not in itself demonstrate class
certification was improper. See Olean, 31 F.4th at 669, 680–
81 (holding that the possibility some class members suffered
no injury does not, by itself, defeat class certification); Just
Film, 847 F.3d at 1120 (“To gain class certification,

4
  Nutramax argues that this is not so because “Plaintiffs’ complaint
asserted claims based not only on the labels, but also representations on
the Cosequin® website and in other media; and Plaintiffs pled alternative
theories of damages beyond the price-premium theory.” But if that were
sufficient to defeat predominance, the rule announced in Tyson Foods
would be rendered meaningless. In almost every case it will be possible
to point to some individual proof that could substitute for the
(purportedly) deficient aggregate proof. Here, however, Plaintiffs have
narrowed the case to their challenge of these specific label claims using
aggregate proof, and that is what the district court properly focused on.
20           LYTLE V. NUTRAMAX LABORATORIES, INC.

Plaintiffs need to be able to allege that their damages arise
from a course of conduct that impacted the class. But they
need not show that each members’ damages from that
conduct are identical.”).
    Nutramax’s argument in favor of its proposed
categorical rule—requiring that a damages model always be
executed prior to class certification—rests almost entirely
upon its misinterpretation of the Supreme Court’s decision
in Comcast Corp. v. Behrend, 569 U.S. 27 (2013), and our
recent en banc decision in Olean. We agree that these cases
demand some assessment of the adequacy of Plaintiffs’
common proof at class certification, but nothing in these
cases requires that Plaintiffs actually prove damages at the
class certification stage or prohibits Plaintiffs from relying
on an unexecuted but reliable damages model.
    In Comcast, plaintiffs put forward four theories of
liability, but the district court certified a class as to only one
of them. 569 U.S. at 31. However, the plaintiffs’ damages
expert—whose model provided the only means of proving
classwide damages—conducted an indivisible analysis
which “did not isolate damages resulting from any one [of
the four] theor[ies] of [liability].” Id. at 32. On appeal, the
defendants argued class certification was improper because
plaintiffs had “failed to attribute damages” to the sole
remaining theory in the case, but the Third Circuit affirmed
the district court’s grant of class certification over this
objection, reasoning that it was an improper “attac[k] on the
merits of the methodology [that had] no place in the class
certification inquiry.” Id.
    The Supreme Court reversed. The Court explained that
plaintiffs’ “model failed to measure damages resulting from
the particular antitrust injury on which petitioners’ liability
            LYTLE V. NUTRAMAX LABORATORIES, INC.            21

in this action is premised.” Id. at 36. This disconnect was
fatal, because it meant plaintiffs could not “establish[] that
damages are capable of measurement on a classwide basis.”
Id. at 34. In other words, where an expert’s damages model
is untethered from plaintiff’s theory of liability such that it
has no possibility of demonstrating the amount of damages
in a particular case, Comcast holds that a plaintiff may not
rely upon it to show that damages are “capable of
measurement on a classwide basis.” Id. Notably, the
plaintiffs in Comcast “never challenged” the “need to prove
damages on a classwide basis” in order to demonstrate
predominance. Id. at 42 (Ginsburg, J., dissenting).
    Nutramax contends that, as in Comcast, permitting
Plaintiffs here to rely on an unexecuted damages model
would “reduce Rule 23(b)(3)’s predominance requirement to
a nullity,” and would “not establish that the requirements of
Rule 23 are satisfied ‘in fact.’” This is an overreading of
Comcast. That decision has generally been construed to
stand for the unremarkable proposition that “plaintiffs must
be able to show that their damages stemmed from the
defendant’s actions that created the legal liability.” Leyva v.
Medline Indus. Inc., 716 F.3d 510, 514 (9th Cir. 2013).
Indeed, even after Comcast, we have repeatedly reaffirmed
that class treatment may be appropriate even where damages
must be assessed on an individualized basis. See Vaquero v.
Ashley Furniture Indus., Inc., 824 F.3d 1150, 1155 (9th Cir.
2016); Pulaski & Middleman, LLC v. Google, Inc., 802 F.3d
979, 987 (9th Cir. 2015). Contrary to Nutramax’s contention,
the possibility that Dr. Dubé’s analysis might reveal
damages with respect to some, but not all, of the challenged
statements does not create “the problem that manifested in
Comcast,” because, as explained above, the structure of the
conjoint analysis allows a damages figure to be associated
22          LYTLE V. NUTRAMAX LABORATORIES, INC.

with each challenged statement. The same was not true in
Comcast, where plaintiffs’ damages model, again, did not
isolate damages between any of plaintiffs’ theories of
liability. See Comcast, 569 U.S. at 32.
    Nutramax’s reliance on Olean is similarly unavailing. In
Olean, plaintiffs brought an antitrust class action against the
major U.S. packaged tuna suppliers, alleging that they
engaged in unlawful price fixing. 31 F.4th at 661–62. The
appeal centered around whether the district court properly
granted class certification based upon plaintiffs’ expert
evidence showing antitrust impact. Id. We analyzed each of
the plaintiffs’ damages models and the defendants’
objections to those models, and ultimately concluded that the
district court did not abuse its discretion in certifying the
class. See id. at 670–85.
    Nothing in Olean requires that an expert actually execute
a damages model before it can be relied on. In describing the
legal standard, Olean made clear that the focus is on “‘the
method or methods by which plaintiffs propose to use the
[class-wide] evidence to prove’ the common question in one
stroke,” and “a district court is limited to resolving whether
the evidence establishes that a common question is capable
of class-wide resolution, not whether the evidence in fact
establishes that plaintiffs would win at trial.” Olean, 31 F.4th
at 666–67 (quoting In re Hydrogen Peroxide Antitrust Litig.,
552 F.3d at 313). While Olean suggested that a district court
must “[w]eigh[] conflicting expert testimony” and
“consider[] factors that may undercut the model’s
reliability,” id. at 666, 683, this does not categorically
require an expert to execute the expert’s model before it may
be relied upon. Rather, as explained in more detail below,
the fact that an expert’s model has not yet been executed is
simply one factor that must be considered.
             LYTLE V. NUTRAMAX LABORATORIES, INC.             23

    Nutramax cites snippets of Olean to argue that
“[e]vidence is ‘capable of resolving a common issue’ where
each class member could rely on it at trial and the evidence
‘could reasonably sustain a jury verdict in favor of the
plaintiffs, even though a jury could still decide that the
evidence was not persuasive.’” But this suggests that Olean
required the same showing necessary to avoid summary
judgment, which it plainly did not. Indeed, Nutramax’s
reading of the “could reasonably sustain a jury verdict”
language in Olean would mean that we took as mandatory
the Supreme Court’s suggestion that class certification might
sometimes overlap with the merits inquiry and would make
a determination of the merits required, which would be
contrary to settled law. It is settled that the question at class
certification is not whether plaintiffs have put forward
evidence capable of sustaining a jury verdict, but rather
whether plaintiffs have shown enough to satisfy FRCP 23.
To require an actual weighing, at class certification, of
whether plaintiffs’ evidence could sustain a jury verdict
would collapse the class certification and summary
judgment inquiries in precisely the manner Tyson Foods
warns against. 577 U.S. at 457 (noting that failures of proof
that are common to the class should be engaged “as a matter
of summary judgment, not class certification”); see also
Miles v. Kirkland’s Stores Inc., 89 F.4th 1217, 1224 n.2 (9th
Cir. 2024) (noting a “merits question that should be left for
summary judgment or trial, not [resolved] at class
certification”).
    Finally, Nutramax contends that where it is uncertain
that a damages model will show any injury at all, permitting
a class to be certified and sending notice to class members
would be an inefficient use of resources. Plaintiffs respond
that executing a conjoint analysis is extremely expensive and
24             LYTLE V. NUTRAMAX LABORATORIES, INC.

time consuming, so that requiring Plaintiffs to do so before
the precise contours of the class have been established would
risk wasting resources, not save them. We regard these
competing speculations as largely irrelevant to determining
what Rule 23 does or does not require. And since the
determination of class certification is largely within the
discretion of the district court, it is worth noting that the vast
majority of district courts in our circuit to consider the
question have found that a damages expert need not fully
execute his or her proposed conjoint analysis before it can
be relied upon at class certification. See, e.g., Gunaratna v.
Dennis Gross Cosmetology LLC, 2023 WL 5505052, at *19
(C.D. Cal. Apr. 4, 2023); Bailey v. Rite Aid Corp., 338
F.R.D. 390, 408 n.14 (N.D. Cal. 2021); Testone v. Barlean’s
Organic Oils, LLC, 2021 WL 4438391, at *17 (S.D. Cal.
Sept. 28, 2021); Guido v. L’Oreal, USA, Inc., 2014 WL
6603730, at *13–14 (C.D. Cal. July 24, 2014). 5 This

5
 While there are district court cases that have found a proposed conjoint
analysis to be insufficiently detailed or thorough to support a finding of
predominance, they also do not support the categorical rule Nutramax
proposes. Rather, they reflect the unremarkable proposition that an
underdeveloped expert model is far less likely to be able to establish that
a particular element is susceptible to common proof. See In re ConAgra
Foods, Inc., 302 F.R.D. 537, 552 (C.D. Cal. 2014) (rejecting proposed
conjoint survey where expert simply “offer[ed] a basic description of the
manner in which hedonic regression and conjoint analysis operate, and
assert[ed] that the exact specifications [the expert’s analysis would] use
will be solidified as discovery progresses”); Miller v. Fuhu Inc., 2015
WL 7776794, at *21-22 (C.D. Cal. Dec. 1, 2015) (concluding that
expert’s testimony that “it is possible and practical to design and
conduct” a conjoint analysis was insufficient to establish predominance
where expert had not designed such a survey). Indeed, in ConAgra, the
district court subsequently granted class certification based upon a
“proposed conjoint analysis” once the expert had provided a more fully
              LYTLE V. NUTRAMAX LABORATORIES, INC.                  25

common practice weighs against imposing the categorical
rule Nutramax requests.
                                  B.
    Having concluded that there is no categorical prohibition
on a district court relying on an unexecuted damages model
to certify a class, we must nevertheless determine whether,
on the facts of this case, it was error for the district court to
grant certification. In particular, Nutramax argues that the
district court erred in concluding that Dr. Dubé’s opinions
were sufficiently reliable to satisfy FRE 702 or FRCP 23.
    Nutramax argues that because Dr. Dubé had not yet
obtained all of the data necessary to fully execute his model,
the district court could not have found that his opinion
satisfied the requirements of FRE 702 that his testimony be
“based on sufficient facts or data.” Fed. R. Evid. 702(b). But
here again, we think Nutramax confuses a class certification
proceeding with a summary judgment motion. As applied to
class certification where the issues are commonality and
predominance, the Rule 702(b) question concerns whether
the data suffices to show that a common question
predominates over individual issues, not whether the
subsequently executed model applied to a more complete
dataset would then meet the requirements of 702(b) as
applied to a summary judgment motion. By the same token,
we do not agree with Nutramax that the “rigorous analysis”

developed methodology. See In re ConAgra Foods, Inc., 90 F. Supp. 3d
919, 954 (C.D. Cal. 2015); see also Vizcarra v. Unilever United States,
Inc., 2023 WL 2364736, at *16–18 (N.D. Cal. Feb. 24, 2023) (noting the
court had previously rejected un-executed conjoint analysis based on
methodological flaws, but granting class certification based on revised
analysis that corrected those flaws, even where the survey had not been
fully executed).
26            LYTLE V. NUTRAMAX LABORATORIES, INC.

required at the class certification stage means that every
expert opinion offered at that stage must be subjected to a
full evidentiary hearing to see if each such opinion meets the
requirements of Daubert v. Merrell Dow Pharmaceuticals,
Inc., 509 U.S. 579 (1993).
                                  1.
    The manner and extent to which the Daubert framework
applies at the class certification stage is an unsettled
question. A leading treatise has suggested that there is at
least some divergence among the Circuits on this question,
with some employing a “full” Daubert inquiry and others
employing a more limited one. See 3 Newberg and
Rubenstein on Class Actions § 7:24 (6th ed. 2022). 6
    Our own precedent has somewhat oscillated between
these two approaches. In Ellis v. Costco Wholesale Corp.,
we affirmed a district court’s application of the Daubert
standard at the class certification stage. 657 F.3d 970, 982–
83 (9th Cir. 2011); see also 3 Newberg and Rubenstein on
Class Actions § 7:24 (6th ed. 2022) (characterizing Ellis as
adopting a full Daubert test). Similarly, in Olean, we stated
in dicta that “[i]n a class proceeding, defendants may
challenge the reliability of an expert’s evidence under
Daubert,” although the defendants in Olean did not actually
raise a Daubert challenge. 31 F.4th at 665 n.7. In Sali v.
Corona Regional Medical Center, however, we noted that
while “a district court should evaluate admissibility under
the standard set forth in Daubert,” whether testimony is
admissible under that standard is “not . . . dispositive,” but

6
  The Supreme Court originally granted certiorari in Comcast to resolve
this question, but ultimately resolved the case on other grounds once it
became apparent the question was not properly presented. Comcast, 569
U.S. at 39–40 (Ginsburg, J., dissenting).
            LYTLE V. NUTRAMAX LABORATORIES, INC.             27

instead “should go to the weight that evidence is given at the
class certification stage.” 909 F.3d at 1006. We cited with
approval the Eighth Circuit’s decision in In re Zurn Pex
Plumbing Products Liability Litigation, which is the leading
decision endorsing a more limited Daubert inquiry. Id. at
1004; see Cox v. Zurn Pex, Inc. (In re Zurn Pex Plumbing
Prods. Liab Litig.), 644 F.3d 604, 613 (8th Cir. 2011) (“The
main purpose of Daubert exclusion is to protect juries from
being swayed by dubious scientific testimony. That interest
is not implicated at the class certification stage where the
judge is the decision maker.”).
    We think that, at least for purposes of this case, the
distinction between a “full” and “limited” Daubert inquiry is
a function of what aspect of FRCP 23 is being addressed.
Here, the question under FRE 702 is whether the model that
the plaintiffs’ expert is offering on the issues of commonality
and predominance is reliable for FRCP 23 purposes.
Accordingly, such Daubert factors as peer review of the
proffered model may be highly relevant, while others, such
as known error rate, may be more applicable to the later-
executed results of the test. Daubert itself stressed that its
suggested factors were simply illustrative and needed to be
applied flexibly, and this surely means applying them only
to the extent helpful to the issue at hand. See Daubert, 509
U.S. at 593–94 (noting that “[t]he inquiry envisioned by
Rule 702 is . . . a flexible one” and disclaiming any intent “to
set out a definitive checklist or test”).
    Thus, for example, whether a “full” or “limited” Daubert
analysis should be applied may depend on the timing of the
class certification decision. If discovery has closed and an
expert’s analysis is complete and her tests fully executed,
there may be no reason for a district court to delay its
assessment of ultimate admissibility at trial. By contrast,
28          LYTLE V. NUTRAMAX LABORATORIES, INC.

where an expert’s model has yet to be fully developed, a
district court is limited at class certification to making a
predictive judgment about how likely it is the expert’s
analysis will eventually bear fruit. This still requires
determining whether the expert’s methodology is reliable, so
that a limited Daubert analysis may be necessary, but the
more full-blown Daubert assessment of the results of the
application of the model would be premature.
    Here, we are satisfied that the district court’s limited
Daubert analysis was sufficient for the immediate purposes.
As the district court expressly recognized, “the court
considers only if expert evidence is useful in evaluating
whether class certification requirements have been met,” and
for that purpose a more limited Daubert inquiry may be
sufficient. This is consistent with the Supreme Court’s
general rule that “[m]erits questions may be considered to
the extent—but only to the extent—that they are relevant to
determining whether the Rule 23 prerequisites for class
certification are satisfied.” Amgen, 568 U.S. at 466.
    In finding that the prerequisites of FRE 702 were met for
FRCP 23 purposes, the district court relied on Dr. Dubé’s
unchallenged       credentials,   Dr. Dubé’s      review     of
documentary evidence and marketing data, the fact that
“[c]onjoint surveys, like the one proposed by [Dr. Dubé], are
a well-established method for measuring class-wide
damages in CLRA mislabeling cases,” and the fact that
Dr. Dubé had successfully performed conjoint analyses in
prior cases similar to this. It is true Dr. Dubé has not
collected all of the necessary data to perform his calculations
in the instant case, but implicit in Dr. Dubé’s opinion—
which the district court credited—is the conclusion that he
would be able to obtain such information, and Nutramax
offers no reason to think he would be unable to do so. Nor,
             LYTLE V. NUTRAMAX LABORATORIES, INC.             29

as explained below, has Nutramax shown either that
Dr. Dubé’s methodology is flawed or that there is a
likelihood that he will improperly apply that method to the
facts. In light of the foregoing, we cannot say that the district
court abused its discretion in rejecting Nutramax’s Daubert
challenge to Dr. Dubé’s opinion.
                               2.
    Nutramax also argues that, even if an unexecuted
damages model may in some circumstances support class
certification, on the facts of this case Dr. Dubé’s model is
too underdeveloped to satisfy the “rigorous analysis”
required under FRCP 23. Nutramax contends that Dr. Dubé
has not designed the survey questionnaire, has not
determined the precise demographic makeup of the
individuals to be surveyed, has not selected all of the
parameters for his model, and lacks certain data needed to
finalize his calculations. Plaintiffs respond that Dr. Dubé has
in fact fully designed the conjoint analysis and the
methodology behind it, including by identifying the target
population, analyzing economic data to determine the
structure of the market, and specifying the mathematical
analysis he will perform on the survey results. While
Plaintiffs acknowledge Dr. Dubé has not yet programmed
the survey (i.e., written the questions), they cite to
Dr. Dubé’s testimony describing this as merely “an
implementation detail,” and argue that it makes sense not to
finalize the survey questions until the exact scope of the class
is known. In short, according to Plaintiffs, the survey is fully
designed and all that remains is for it to be executed.
    As already discussed above, Plaintiffs may rely on an
unexecuted damages model to demonstrate that damages are
susceptible to common proof. To be sure, the fact the model
30            LYTLE V. NUTRAMAX LABORATORIES, INC.

has not been executed remains relevant. Olean makes clear
that “[t]he determination whether expert evidence is capable
of resolving a class-wide question in one stroke may include
‘[w]eighing conflicting expert testimony’ and ‘[r]esolving
expert disputes’ where necessary to ensure that Rule
23(b)(3)’s requirements are met.” 31 F.4th at 666 (internal
citation omitted) (quoting In re Hydrogen Peroxide, 552
F.3d at 323–24). This assessment of a “model’s reliability”
required by Olean goes beyond the Daubert analysis, and the
fact that an expert’s model is sufficiently reliable to meet the
standard of FRE 702 as applied to a FRCP 23 determination
may not be sufficient to satisfy the standard. See Ellis v.
Costco Wholesale Corp., 657 F.3d 970, 982 (9th Cir. 2011)
(suggesting FRCP 23 requires a distinct analysis beyond an
assessment of admissibility under Daubert); Olean, 31 F.4th
at 665–66 nn. 7, 9. Rather, the district court must also probe
the likelihood that the model will be capable of generating
common answers. A district court may not, however,
“decline certification merely because it considers plaintiffs’
evidence relating to the common question to be unpersuasive
and unlikely to succeed.” Id. at 667. 7
    In applying this test to an unexecuted damages model,
the question a district court must ask is whether the model

7
  Olean gave the following examples of expert evidence that, while
otherwise admissible under Daubert, might be unable to generate
common answers: where “the expert evidence was inadequate to prove
an element of the claim for the entire class [i.e., is not common to all];
where the damages evidence was not consistent with the plaintiffs’
theory of liability; where the evidence contained unsupported
assumptions; or where the evidence demonstrated nonsensical results
such as false positives, i.e., injury to class members who could not
logically have been injured by a defendant’s conduct.” Id. at 666 n.9
(internal citations omitted).
              LYTLE V. NUTRAMAX LABORATORIES, INC.                    31

will likely be able to generate common answers at trial. The
fact that a model is underdeveloped may weigh against a
finding that it will provide a reliable form of proof. Merely
gesturing at a model or describing a general method will not
suffice to meet this standard. Rather, plaintiffs—or their
expert—must chart out a path to obtain all necessary data
and demonstrate that the proposed method will be viable as
applied to the facts of a given case. 8
     Here, the district court recognized that Plaintiffs were
required to “show that damages are capable of measurement
on a class-wide basis,” while acknowledging they may do so
without executing the model. On appeal, Nutramax raises a
flurry of attacks on the reliability of Dr. Dubé’s model that
were never presented to the district court. While Nutramax
referenced the underdeveloped nature of Dr. Dubé’s model
throughout its briefing below, the only such argument it
developed with any thoroughness was the contention that
Dr. Dubé lacked critical data needed to complete his
analysis. Since we cannot say that the district court abused
its discretion in failing to consider arguments with which it
was not presented, see Van v. LLR, Inc., 61 F.4th 1053, 1066
n.9 (9th Cir. 2023) (“An issue cannot form part of the district
court’s class certification decision if it was never raised at

8
  Plaintiffs’ briefing on appeal seems to advance a rule that merely
putting forward a viable method is sufficient. To the extent that is
Plaintiffs’ position, we disagree. Even where a method is otherwise valid
and reliable under FRE 702, it may nonetheless fail to produce common
answers for any number of reasons, such as when the model does not
apply in a manner common to the class. Hence, we underscore that the
ultimate inquiry is whether a proposed model is likely to provide
common answers at trial.
32             LYTLE V. NUTRAMAX LABORATORIES, INC.

the class certification stage.” (cleaned up)), we focus our
analysis on those matters considered by the district court. 9
    With respect to the data Dr. Dubé had not yet collected,
the district court acknowledged defendant’s argument but
credited Dr. Dubé’s implicit conclusion that he would be
able to obtain such data prior to trial. Nutramax has not
convincingly demonstrated that the district court erred in
reaching this conclusion.
    Nutramax’s other attacks on Dr. Dubé’s methodology, to
the extent they were presented to the district court, fare no
better. As the district court observed, conjoint analysis is a
well-accepted technique that is frequently used to establish
damages in CLRA actions. See, e.g., Briseno v. ConAgra
Foods, Inc., 674 F. App’x 654, 657 (9th Cir. 2017)
(describing conjoint analysis as a “well-established damages
model”); Hadley v. Kellogg Sales Co., 324 F. Supp. 3d 1084,
1107 (N.D. Cal. 2018) (“[C]onjoint analysis is a well-
accepted economic methodology.” (quoting In re Dial
Complete Mktg. & Sales Pracs. Litig., 320 F.R.D. 326, 331
(D.N.H. 2017)). Where an expert’s proposed method is
novel or untested, it makes sense to demand a greater degree
of specificity and completeness before it is relied upon to
certify a class. See In re New Motor Vehicles Canadian Exp.

9
  In particular, on appeal Nutramax relies heavily upon the rebuttal report
of their expert, Dr. Toubia, to challenge the reliability of Dr. Dubé’s
methodology. Had Dr. Toubia’s report been fairly presented to the
district court as a basis for denying class certification, it might have been
error for the district court to not address it. See Olean, 31 F.4th at 666
(suggesting a district court must “[r]esolv[e] expert disputes” at class
certification). However, our review of the record reveals that Nutramax
never attempted to use Dr. Toubia’s rebuttal report to attack Dr. Dubé’s
model, and instead cited Dr. Toubia’s rebuttal report only a single time,
and for an entirely unrelated proposition.
             LYTLE V. NUTRAMAX LABORATORIES, INC.              33

Antitrust Litig., 522 F.3d 6, 26–30 (1st Cir. 2008) (finding
that “novelty and complexity of the theories advanced” by
plaintiffs and their expert made certification of a class based
upon incomplete model less appropriate). By contrast, here
there is no dispute that a conjoint analysis is capable of
measuring classwide damages, at least in the abstract, and
the only real question at this stage is whether Dr. Dubé will
properly apply the method to the facts of the case.
     Nutramax cites a variety of potential errors Dr. Dubé
might commit in executing his damages model. For example,
Nutramax argues “the precise wording of a questionnaire is
critical” and could “bias[] the results,” and that “assumptions
underlying [his] economic model” may not account for real-
world factors. While unanswered questions such as these,
and the attendant possibility of errors, are certainly relevant,
Nutramax offers no reason to think that Dr. Dubé will
commit any of these errors. Dr. Dubé’s qualifications are
undisputed, he has successfully conducted conjoint analyses
in the past, and Dr. Dubé testified he did not “envision
anything particularly unique about this survey.” The
speculative possibility that Dr. Dubé might slip up in
executing his model, standing alone, is insufficient to defeat
class certification. See Sali, 909 F.3d at 1004–05 (“Neither
the possibility that a plaintiff will be unable to prove his
allegations, nor the possibility that the later course of the suit
might unforeseeably prove the original decision to certify the
class wrong, is a basis for declining to certify a class which
apparently satisfies [Rule 23].” (quoting Blackie v. Barrack,
524 F.2d 891, 901 (9th Cir. 1975)). 10

10
   This is especially true here given that “[c]lass wide damages
calculations under the . . . CLRA are particularly forgiving” and
34            LYTLE V. NUTRAMAX LABORATORIES, INC.

    Accordingly, the record was sufficient to support the
district court’s conclusion that Dr. Dubé’s model is capable
of showing damages on a class wide basis.
                                  C.
    As the above discussion makes clear, it is not required
that a plaintiff’s expert must execute their damages model
prior to class certification provided it is shown that the model
provides a reliable and adequate method for calculating
damages. We do, however, think it important to make clear
that a plaintiff may not avoid ultimate scrutiny of the
admissibility of their experts’ final opinions simply by
declining to develop those opinions in advance of class
certification. Accordingly, on remand, Nutramax must be
given the opportunity in advance of trial to test the
sufficiency and reliability of Dr. Dubé’s model once it has
been fully executed, including through a motion for
summary judgment and/or a renewed Daubert motion.
                                 IV.
    The second broad issue raised by Nutramax on appeal is
whether the district court erred in concluding that common
questions predominated with respect to the element of
reliance. California’s CLRA prohibits “unfair methods of
competition and unfair or deceptive acts or practices.” Cal.
Civ. Code § 1770(a). To bring a CLRA claim, a plaintiff
must show (1) the defendant engaged in deceptive conduct
and (2) the deception caused plaintiff harm. Stearns, 655
F.3d at 1022. However, under the CLRA, “[c]ausation, on a
classwide basis, may be established by materiality. If the

“require[] only that some reasonable basis of computation of damages be
used.” Nguyen v. Nissan N. Am., Inc., 932 F.3d 811, 818 (9th Cir. 2019)
(quoting Lambert, 870 F.3d at 1183).
             LYTLE V. NUTRAMAX LABORATORIES, INC.             35

trial court finds that material misrepresentations have been
made to the entire class, an inference of reliance arises as to
the class.” Id. (quoting In re Vioxx Class Cases, 180 Cal.
App. 4th 116, 129 (2009)). A misrepresentation is material
“if a reasonable [person] would attach importance to its
existence or nonexistence in determining his choice of action
in the transaction in question[.]” Id.
      Because materiality (and, hence, in this case reliance)
may be proved by reference to an objective, reasonable
consumer standard, reliance under the CLRA is generally
susceptible to common proof. See Noel v. Thrifty Payless,
Inc., 17 Cal. App. 5th 1315, 1334 (2017) (“When the
consumer shows the complained-of misrepresentation would
have been material to any reasonable person, he or she has
carried the burden of showing actual reliance and causation
of injury for each member of the class.”), rev’d on other
grounds, 7 Cal. 5th 955 (2019); Stearns, 655 F.3d at 1022;
Bradach v. Pharmavite, LLC, 735 F. App’x 251, 254 (9th
Cir. 2018) (“Under California law, class members in CLRA
. . . actions are not required to prove their individual reliance
on the allegedly misleading statements. Instead, the standard
. . . is whether members of the public are likely to be
deceived. For this reason, . . . [CLRA] claims are ideal for
class certification because they will not require the court to
investigate class members’ individual interaction with the
product.” (internal quotation marks and citations omitted)).
However, while materiality can support an inference of
reliance, that does not necessarily mean that the inference
will hold as to the entire class, such that common questions
predominate. “If the misrepresentation or omission is not
material as to all class members, the issue of reliance ‘would
vary from consumer to consumer’ and the class should not
36             LYTLE V. NUTRAMAX LABORATORIES, INC.

be certified.” Stearns, 665 F.3d at 1022–23 (quoting Vioxx,
180 Cal. App. 4th at 129).
    The district court cited the correct legal standard, noting
that materiality can be used to establish reliance under the
CLRA, while also acknowledging that the presumption is
rebuttable insofar as “reliance would vary from consumer to
consumer.” Nutramax nonetheless contends the district court
committed legal error by finding “the ‘objective test’ used
for materiality rendered materiality and thus causation
inherently a common issue.” Read in context, we do not
think the district court applied an incorrect, irrebuttable
presumption as Nutramax suggests. Rather, the observation
that materiality and causation are “inherently common
issues” was made only after the district court considered the
relevant evidence of materiality and concluded it supported
an application of the presumption. We therefore review the
district court’s findings on this issue for abuse of discretion.
See Sali, 909 F.3d at 1002. 11
    Plaintiffs presented ample evidence to show that the
challenged statements would be materially misleading to a
reasonable consumer. To demonstrate that a reasonable
consumer would have understood the challenged statements
to have promised that the product would improve a dog’s
joint health, Plaintiffs cited the testimony of the named
plaintiffs, the testimony of their advertising expert,
Silverman, and the survey results of Nutramax’s own expert,
Dr. Scott, which indicated that the near-universal

11
   We also do not think the district court committed legal error when it
cited the rule that “a plaintiff is not required to show that the challenged
statement is the ‘sole or even the decisive cause’ influencing the class
members’ decisions to buy the challenged products.” As explained
below, this statement is consistent with California law.
              LYTLE V. NUTRAMAX LABORATORIES, INC.                    37

understanding of Cosequin’s purpose was that it would
“improve/help/maintain      mobility,    flexibility,   joint
health/support.” This understanding, caused by Nutramax’s
packaging statements, was, according to Plaintiffs’ experts,
false and misleading because there is no evidence that
Cosequin improves a dog’s joint health. The district court
credited all of this evidence and expressly found that it
“outweighed” the contrary evidence presented by
defendants’ experts, including Dr. Scott. Nutramax has not
shown that this conclusion was an abuse of discretion. The
district court thus correctly found that Plaintiffs had
demonstrated that the presumption of reliance applied. 12
    Nutramax nonetheless argues that it put forward
sufficient evidence to rebut the presumption, and the district
court erred in concluding otherwise. Nutramax points to
what it describes as “overwhelming evidence that
veterinarians frequently recommend joint supplements,
including Cosequin.” Nutramax similarly cites the results of
Dr. Scott’s survey, which suggests approximately half of
survey respondents decided to purchase Cosequin before
going to a physical store or website. According to Nutramax,
all of this demonstrates that individualized assessments will
be needed to determine whether any given class member
actually relied on the label.
    The fact some class members considered sources of
information other than the packaging in making their

12
   Nutramax argues that Plaintiffs’ evidence of falsity showed only that
Cosequin was unable to treat dogs with arthritis, not that it was totally
ineffective at promoting joint health generally, but Nutramax made this
argument in the court below and it was expressly rejected by the district
court, which credited Plaintiffs’ evidence that “Cosequin has no effect
on joint health.”
38          LYTLE V. NUTRAMAX LABORATORIES, INC.

purchasing decisions does not necessarily undermine
reliance. To establish reliance under the CLRA, a
misrepresentation need not be “the sole or even the decisive
cause of the injury-producing conduct.” Moore v. Mars
Petcare US, Inc., 966 F.3d 1007, 1020 (9th Cir. 2020)
(quoting Kwikset Corp. v. Superior Ct., 246 P.3d 877, 888
(Cal. 2011)). For example, in Moore, we found that “[t]he
fact that vets had prescribed each Plaintiff the pet food—
rather than each discovering the pet food on their own—
[did] not negate the allegation of actual reliance because the
prescription requirement and advertising need not be the sole
or even the decisive cause of the purchase.” Id. at 1020–21.
In other words, Moore rejected the very argument now
advanced by Nutramax, that there can be no reliance where
a veterinarian recommends a product.
    Nutramax attempts to distinguish Moore on the grounds
that it was decided on a motion to dismiss. However, at least
one California appellate court has applied the rule beyond
the motion to dismiss context. See Veera v. Banana
Republic, LLC, 6 Cal. App. 5th 907, 919 (2016) (applying
rule to deny motion for summary judgment). And the model
jury instructions for a CLRA claim promulgated by the
Judicial Council of California similarly indicate that, “[t]o
prove reliance, [name of plaintiff] need only prove that the
representation was a substantial factor in [his/her/nonbinary
pronoun] decision” and “does not need to prove that it was
the primary factor or the only factor in the decision.” Judicial
                 LYTLE V. NUTRAMAX LABORATORIES, INC.                   39

Council of California, Model Civil Jury Instruction No.
4700. 13
    To be sure, the fact that some consumers relied on other
sources of information is relevant to the assessment of
reliance. In an appropriate case, such evidence might be
sufficient to demonstrate that the misrepresentation was not
“a substantial factor” in a large percentage of consumers’
purchasing decisions. But we do not think it was an abuse of
discretion for the district court to find to the contrary here. If
one imagines a counterfactual where the packaging
contained no suggestion that Cosequin benefited a dog’s
joint health, it is entirely plausible that no consumer would
have chosen to purchase the product. See Alvarez v. NBTY,
Inc., 331 F.R.D. 416, 423 (S.D. Cal. 2019) (“Without [the
challenged] statement, no consumer would have a reason to
purchase the Products and would otherwise be purchasing a
random bottle of supplements without any knowledge of
what benefit, if any, the supplements provided.”). Further,
while one of Plaintiffs’ theories of causation is that they

13
     The full instruction reads:
            [[Name of plaintiff]’s harm resulted from [name of
            defendant]’s conduct if [name of plaintiff] relied on
            [name of defendant]’s representation. To prove
            reliance, [name of plaintiff] need only prove that the
            representation was a substantial factor in
            [his/her/nonbinary          pronoun]          decision.
            [He/She/Nonbinary pronoun] does not need to prove
            that it was the primary factor or the only factor in the
            decision.
            If [name of defendant]’s representation of fact was
            material, reliance may be inferred. A fact is material if
            a reasonable consumer would consider it important in
            deciding whether to buy or lease the [goods/services].]
40          LYTLE V. NUTRAMAX LABORATORIES, INC.

would not have purchased the products had they known the
truth, another theory is that they paid more than they
otherwise would have as a result of the misleading
statements. See Hinojos v. Kohl’s Corp., 718 F.3d 1098,
1108 (9th Cir. 2013) (“[T]he CLRA’s ‘any damage’
requirement is a capacious one that includes any pecuniary
damage as well as opportunity costs and transaction costs
that result when a consumer is misled by deceptive
marketing practices.”). If, as Plaintiffs contend, Cosequin
provided no benefits to joint health, it is still more plausible
that the consumers would have paid less had they known the
truth.
    This construction of the reliance requirement comports
with the objectives of the CLRA more generally. The
California legislature has declared that the CLRA “shall be
liberally construed and applied to promote its underlying
purposes, which are to protect consumers against unfair and
deceptive business practices and to provide efficient and
economical procedures to secure such protection.” Cal. Civ.
Code § 1760. Consistent with this remedial objective, we
have suggested that CLRA claims “are ideal for class
certification because they will not require the court to
investigate class members’ individual interaction with the
product.” Bradach, 735 F. App’x at 254 (quotation omitted).
Nutramax’s cramped interpretation of the reliance
requirement, permitting the presumption to be overcome
based upon marginally different interactions with a product
containing a label that is otherwise materially misleading,
would undermine the presumption of reliance and the
capacity to bring CLRA class actions.
    None of the cases that Nutramax cites, finding that the
presumption of reliance was overcome, is to the contrary.
For example, in Stearns v. Ticketmaster Corp., the plaintiffs
             LYTLE V. NUTRAMAX LABORATORIES, INC.             41

sued Ticketmaster for creating a website that misled
individuals who purchased tickets into inadvertently signing
up for an unrelated monthly subscription. 655 F.3d at 1017.
While the district court acknowledged that this practice
likely violated the CLRA, it nevertheless found class
certification inappropriate because the plaintiffs’ proposed
class was too broad. Id. at 1024. We upheld this holding and
explained that materiality was not uniform across the class
because many class members would not have been deceived
by Ticketmaster’s marketing practice and had intentionally
signed up for the subscription. Id.
    Again, in In re Vioxx Class Cases, the “[p]laintiffs
suggest[ed] that Merck hid an increased risk of death,
associated with Vioxx,” which plaintiffs used to support an
inference of reliance. 180 Cal. App. 4th 116, 133 (2009)
(cleaned up). While a risk of death is material in the abstract,
the trial court found class treatment inappropriate because
defendants had introduced “overwhelming evidence” that
materiality varied on an individual basis. Id. For example,
the record contained undisputed evidence that the drug
actually did not increase the risk of death for all of the class
members and that some individuals continued taking the
drug even after learning of the risks in light of its substantial
countervailing benefits. Id. at 133–34.
    Finally, in Fairbanks v. Farmers New World Life Ins.
Co., the plaintiffs alleged that defendant’s marketing
practices surrounding “universal life insurance” were
misleading because the marketing suggested the policies
were “permanent” when in fact the policies were not
permanent and were systematically underfunded. 197 Cal.
App. 4th 544, 553 (2011). The court observed that plaintiffs’
class certification motion “assume[d] that anyone who
purchases universal insurance does so because . . . a
42          LYTLE V. NUTRAMAX LABORATORIES, INC.

universal policy (if sufficiently funded) can be permanent,”
when in fact the record showed there were many other
reasons an individual might purchase a universal insurance
policy unrelated to its supposed permanence. Id. at 565.
Therefore, not all class members would find the
misrepresentations about the policy being “permanent”
material or misleading.
    The common theme unifying each of these cases is that
a sizable portion of the class either were not misled by the
statements or would not have found the misrepresentations
to be material had they known the truth. Here, by contrast,
Dr. Scott’s own survey indicated that the near-universal
reason class members purchased Cosequin was because it
would “improve/help/maintain mobility, flexibility, joint
health/support.” Indeed, it is difficult to see why else
consumers would purchase this “joint health supplement”
other than to improve their dog’s joint health. For purposes
of class certification, Plaintiffs have adequately
demonstrated that a reasonable consumer would have been
misled into believing Cosequin would improve their dogs’
joint health, when, in fact, Cosequin provided no such
benefits, and that this misrepresentation would have been
material as to the entire class. The district court thus did not
abuse its discretion in concluding reliance may be proven on
a class wide basis.
                              V.
   For the foregoing reasons, we affirm the district court’s
grant of class certification.
     AFFIRMED.