FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

In re: GILEAD SCIENCES SECURITIES        
LITIGATION.


RICK HARTMAN, on behalf of
himself and all others similarly
situated; TRENT ST. CLARE; TERRY               No. 06-16185
JOHNSON,
              Plaintiffs-Appellants,            D.C. No.
                                              CV-03-04999-MJJ
                v.
                                                 OPINION
GILEAD SCIENCES, INC.; JOHN C.
MARTIN; JOHN F. MILLIGAN; MARK
L. PERRY; NORBERT W.
BISCHOFBERGER; ANTHONY
CARRACIOLO; JOHN EICHLER,
            Defendants-Appellees.
                                         
        Appeal from the United States District Court
          for the Northern District of California
         Martin J. Jenkins, District Judge, Presiding

                  Argued and Submitted
        December 6, 2007—San Francisco, California

                     Filed August 11, 2008

Before: Alex Kozinski, Chief Judge, Michael Daly Hawkins,
          and Robert E. Cowen,* Circuit Judges.

   *The Honorable Robert E. Cowen, Senior United States Circuit Judge
for the Third Circuit, sitting by designation.

                               10319
10320   IN RE GILEAD SCIENCES SECURITIES LITIGATION
               Opinion by Judge Hawkins
10322     IN RE GILEAD SCIENCES SECURITIES LITIGATION


                         COUNSEL

Susan K. Alexander (briefed and argued), Lerach, Coughlin,
Stoia, Geller, Rudman & Robbins LLP, San Francisco, Cali-
fornia, for the plaintiffs-appellants.

John C. Dwyer (briefed and argued), Grant Fondo and Jeffrey
M. Kaban (appeared only), Cooley, Godward, Kronish, LLP,
Palo Alto, California, for the defendants-appellees.


                         OPINION

HAWKINS, Circuit Judge:

  A group of individual investors brought this securities fraud
action on behalf of themselves and a proposed class compris-
ing all individuals (collectively, the “Investors”) who pur-
chased Gilead Sciences, Inc.’s (“Gilead”) publicly traded
securities between July 14, 2003, and October 28, 2003
              IN RE GILEAD SCIENCES SECURITIES LITIGATION            10323
(“class period”). They allege that Gilead misled the investing
public by representing that demand for its most popular prod-
uct was strong without disclosing that unlawful marketing
was the cause of that strength.

   The district court dismissed under Rule 12(b)(6) of Civil
Procedure, holding that the Investors failed to sufficiently
allege loss causation. We have jurisdiction under 28 U.S.C.
§ 1291, and we reverse.

            FACTS AND PROCEDURAL HISTORY

I.       The Complaint’s Allegations

   The Investors’ Fourth Amended Complaint (“complaint”)
alleges violations of sections 10(b) and 20(a) of the Securities
Exchange Act of 1934, 15 U.S.C. §§ 78j(b), 78t(a), and SEC
Rule 10b-5, 17 C.F.R. § 240.10b-5. The complaint names as
defendants Gilead and some of its top officers (“Officers”).

  Taking its allegations as true, the complaint tells the fol-
lowing story about Gilead and its marketing practices.1

   Gilead is a biopharmaceutical company that specializes in
developing and marketing treatments for life-threatening dis-
eases. One of the company’s commercial products is Viread,
an antiretroviral agent used in combination with other drugs
to treat HIV.

  Gilead’s fortunes, as reflected in its stock price, depended
heavily on Viread’s commercial success. Sales of Viread
amounted to about 65% of Gilead’s total revenues at all rele-
     1
    We recount only those facts necessary for understanding the loss cau-
sation issue. The complaint, which spans over seventy pages, offers much
greater detail. Because we disagree with the district court on the issue, we
frequently quote the complaint to demonstrate that the Investors did in fact
explicate the causal logic underlying their theory.
10324       IN RE GILEAD SCIENCES SECURITIES LITIGATION
vant times of this action. “Wall Street analysts looked to sales
of Viread, Gilead’s most important and most promoted drug,
to gauge whether the Company’s business was on track and
growing. If Gilead failed to publicly report healthy, growing
Viread sales, its stock price would be greatly diminished.”

   Although Gilead had a clear incentive to aggressively pro-
mote Viread, it was required to comply with federal law,
including the Food and Drug Administration’s (“FDA”) mar-
keting regulations. Generally, those regulations prohibit the
marketing of drugs for non-FDA-approved uses, commonly
referred to as “off-label” uses. “For example, it would be con-
sidered off-label for a company to market a FDA-approved
HIV/AIDS drug as also being effective for fighting Hepatitis
B infection . . . if such use of the drug had not been reviewed
and approved by the FDA and included in the” drug’s FDA-
approved package labeling. While physicians are free to pre-
scribe drugs for off-label uses,2 they rely on the FDA-
approved prescribing information to determine which drugs
can be used safely and effectively by patients with specific
health problems. The FDA approved Viread for use in
approximately 40% of the available HIV patient pool. Repeat-
edly violating the FDA’s off-label marketing regulations in an
effort to have Viread prescribed to some of the remaining
60% of available HIV patients, Gilead and its officers:

      implemented a scheme to promote and market
      Viread with off-label, false, and misleading state-
      ments in violation of the Federal Food, Drug, and
      Cosmetic Act. In order to gain market share, artifi-
      cially increase perceived demand, and increase sales,
      Gilead officers, executives, and clinical personnel,
  2
   See 21 U.S.C. § 396; Buckman Co. v. Plaintiffs’ Legal Comm., 

, 350-51 & n.5 (2001) (explaining that “the FDA is charged with
the difficult task of regulating the marketing and distribution of medical
devices without intruding upon decisions statutorily committed to the dis-
cretion of health care professionals”).
            IN RE GILEAD SCIENCES SECURITIES LITIGATION              10325
      with the express knowledge and approval of the
      [Officers], routinely and consistently provided Gile-
      ad’s sales and marketing team with off-label infor-
      mation and encouraged, expected, and directed them
      to use it to sell Viread . . . .

   Gilead’s management began preparing Gilead’s sales staff
for off-label marketing as early as September 2001, one
month before Viread received FDA approval. Management
continued to encourage off-label marketing throughout 2002
and the first half of 2003.

   These training efforts produced their intended effect.
According to two confidential witnesses who served as Gilead
salespeople,3 Viread “off-label marketing took three forms:
(1) marketing to HIV patients co-infected with Hepatitis B;
(2) marketing Viread as a first-line or initial therapy for HIV
infection; and (3) marketing against Viread’s safety profile.”
Ultimately, 75% to 95% of Viread sales resulted from off-
label marketing efforts.

   The company and its Officers emphasized to the public that
they carefully complied with federal and state regulations,
when in fact they knew that they were acting unlawfully by
aggressively marketing Viread for off-label uses.

   The first sign of trouble came on March 14, 2002, when the
FDA sent an “Untitled Letter” to Gilead that accused the com-
pany of understating the risks of Viread—a form of improper
off-label marketing. The letter ordered Gilead to “immedi-
ately cease” this practice. On March 21, 2002, per the FDA’s
request, Gilead sent a reply that acknowledged receipt of the
FDA’s letter and agreed to immediately stop off-label market-
  3
   One of the confidential witnesses served as “a member of Gilead’s
Field Marketing Advisory Committee, a select committee of Gilead sales
and marketing staff that periodically met to discuss theories and strategies
for marketing and selling Viread.”
10326     IN RE GILEAD SCIENCES SECURITIES LITIGATION
ing. This was not done. In fact, Gilead’s off-label marketing
increased, either at the Officers’ direction or with their knowl-
edge and tacit encouragement.

   By June 2003, Gilead’s off-label marketing put it in the
position to raise Viread’s price. Consistent with standard
industry practice, Gilead informed national drug wholesalers
of this plan in advance of the price increase. The wholesalers
(there are the three major ones that purchase approximately
ninety percent of drug manufacturers’ drugs) typically stock-
pile drugs in advance of price increases so that they can resell
at a higher price to retailers after the increase takes effect.

   Because Gilead had “illegally inflated sales and artificially
inflated demand for Viread, the major drug wholesalers stock-
piled mass quantities of Viread in advance of the June 2003
price increase. This wholesaler stockpiling would not have
occurred but for the off-label marketing and the resulting cre-
ation of an artificially increased demand for Viread.” The
stockpiling furthered Gilead’s fraudulent scheme by confirm-
ing “the impression that Viread was in high demand and that
Gilead’s financial and operational results were strong.”

   On July 14, 2003, Gilead issued a press release announcing
that it anticipated its second quarter financial results would
exceed analysts’ expectations, and explaining that the compa-
ny’s success “was driven primarily by strong sales growth of
Viread . . . . Increasing Viread sales reflect broader prescrib-
ing patterns in all commercial markets, as well as increases in
U.S. wholesaler inventory levels in the second quarter in
anticipation of a Viread price increase.”

  These statements were materially false and misleading
because Gilead and its Officers’ “marketing and promotional
activities for Viread were not in compliance with FDA
approved guidelines, violated federal laws, and created seri-
ous public health and safety implications for Viread users.”
Gilead’s promotional scheme was designed to, and did, create
              IN RE GILEAD SCIENCES SECURITIES LITIGATION               10327
the impression that demand for Viread was strong. This cam-
paign was misleading, however, because it was unlawful off-
label marketing that was driving prescription volume4 —and
Gilead had already been ordered to cease such marketing.

   While securities analysts, for the most part, reacted favor-
ably to the July 14, 2003, press release, Gilead and its Offi-
cers felt the need to respond to some analysts’ concern that
second quarter revenues were primarily attributable to the
wholesaler stockpiling, and not a result of strong demand. On
the same day that the press release was issued, a Gilead
spokeswoman, acting with the knowledge and approval of
Gilead and its officers, told Bloomberg News that “[t]he main
reason for the jump in Viread sales is an increase in prescrip-
tions, not inventory stocking.” This statement was misleading.
It created the impression that demand for Viread was strong,
which it was, but for reasons that were not well-understood by
the public. Omitting the role of off-label marketing in a press
release highlighting the drug’s success made a true statement
(that demand was strong) also a misleading one.

   Gilead’s financial news had a marked effect on its stock
price. On July 14, the price of Gilead shares closed at $67.25,
up $7.97 from the previous day’s closing price of $59.28 per
share. This 13.4% increase represented a near-record high.

  Some two weeks later, the FDA issued a July 29 Warning
Letter5 that chastised Gilead for statements made by one of its
  4
     The Investors concluded that between $86.7 million and $109.82 mil-
lion of Viread’s $115.6 million in domestic sales during the second quarter
of 2003 could be attributed to off-label marketing.
   5
     The Complaint explains:
      According to the FDA’s website and the FDA’s Regulatory Pro-
      cedures Manual, warning letters such as this are written commu-
      nications from the [FDA] to a company notifying the company
      that the [FDA] considers one or more promotional pieces or prac-
      tices to be illegal. . . . A warning letter is much more serious than
      an untitled letter.
10328     IN RE GILEAD SCIENCES SECURITIES LITIGATION
sales representatives at the 15th National HIV/AIDS Update
Conference in March and April of 2003. The letter stated that
the employee “made oral statements that minimized the risk
information and broadened the indication for Viread.” It
reminded Gilead of the Untitled Letter, expressed the “signifi-
cant public health and safety concerns raised by these repeti-
tive promotional activities,” and ordered Gilead to make
corrective disclosure. Gilead made such disclosure to the con-
ference attendees on November 7, 2003.

   On August 7, 2003, the FDA made public its Warning Let-
ter. Gilead’s shareholders and the investing public did not find
it very significant, though, because they failed to appreciate
the extent of Gilead’s off-label marketing, and thus could not
foresee the letter’s impact on Viread’s sales.

   The public’s underestimation of Viread’s troubles was
reflected in Gilead’s share price. Notwithstanding the public
revelation of the letter, shares closed at higher prices than
they opened on both August 7 and August 8. Indeed, by the
end of August, the stock was trading a few dollars higher than
it had been at the beginning of the month, without having
experienced any significant fluctuations.

   Yet, “[u]nbeknownst to investors, the disclosure of the
FDA Warning Letter had a detrimental effect on Viread sales.
Physicians, now alerted to Gilead’s illegal marketing efforts
and to the safety problems with Viread, were less eager to
prescribe it to their patients.” Competitors invoked the letter
in efforts to persuade physicians to switch from Viread to
their products. In the remaining weeks of August, there was
a “marked drop in prescriptions and sales” of Viread.
Although the Investors lack precise sales figures, a Morgan
Stanley analyst report shows that Viread prescriptions experi-
enced a “sharp drop” in August 2003, followed by “flattened
growth” for the remainder of the third quarter. The prescrip-
tions would have suffered further decline were it not for cer-
           IN RE GILEAD SCIENCES SECURITIES LITIGATION       10329
tain side-effects that made it dangerous for some patients to
discontinue using the drug.

   The wholesalers observed the initial drop in sales and pre-
scriptions of Viread, and the ensuing slow growth. Because
Viread was underperforming relative to the expectations gen-
erated by the second quarter reports, the wholesalers drew
down much more of their excess inventory than they had orig-
inally planned, letting supply of Viread drop to the lowest
level in four quarters, and well below the industry average for
other drugs.

   Although wholesalers recognized Viread’s struggles, the
public continued to misunderstand the significance of the
Warning Letter. Gilead did nothing to correct that misunder-
standing. In its Form 10-Q reporting on the 2003 second quar-
ter, issued on August 14, Gilead persisted in emphasizing the
increased volume of Viread’s second quarter sales without
discussing the role of off-label marketing. Although the Form
10-Q did briefly address the Warning Letter, it failed to reveal
the activities that gave rise to that letter, or the impact the let-
ter would have on sales of Viread.

   The Officers exploited the public’s ignorance. In the days
between the receipt and public disclosure of the Warning Let-
ter, two of the Officers each sold over $3 million worth of
stock. On August 7, the day the FDA disclosed the letter, Gil-
ead’s Senior Vice President/Chief Financial Officer sold
nearly $700,000 worth of shares. Throughout August, while
the market misapprehended Gilead’s impending troubles, the
Officers continued to sell off substantial numbers of shares.
This activity was “unusual and suspicious” because this was
the first month in which all of the Officers sold stock. More
to the point, this was proof that the Officers acted with knowl-
edge or with deliberate recklessness when they issued materi-
ally false and misleading documents and statements that were
disseminated to the investing public.
10330     IN RE GILEAD SCIENCES SECURITIES LITIGATION
   Not until October 28, 2003, did the public finally realize
the impact of the off-label marketing and the Warning Letter.
After the markets closed that day, Gilead issued a press
release detailing third quarter financial results. The public
learned that Viread sales fell significantly below expectations
because there had been substantially more overstocking by
wholesalers than previously reported. Accordingly, third quar-
ter prescriptions were filled by wholesalers’ existing inven-
tory, and wholesalers did not reorder Viread at a
commensurate level. Market analysts attributed the disap-
pointing sales to “lower end-user demand.” That lower end-
user demand, as noted, was a direct result of the Warning Let-
ter, which had exposed Gilead’s unlawful off-label marketing
efforts to physicians.

   The market was “stunned” by the third quarter results.
Share prices closed at $59.46 on October 28, before the press
release was circulated. It may be the case that the market had
already begun to slowly incorporate the information regarding
Viread’s off-label marketing into the share price. But the
third-quarter earnings release made the effect of that informa-
tion inescapably clear. The day after the press release was
issued, trading volume of Gilead shares was up 1,400% from
its average daily level. The day opened with Gilead’s price
per share at $50.69, and closed with a price of $52 per share,
a 12% decrease from the previous day’s closing price.

  Summing it all up,

       At all relevant times, the material misrepresenta-
    tions . . . directly or proximately caused or were a
    substantial contributing cause of the damages sus-
    tained by [the Investors]. . . . [Gilead and the Offi-
    cers] made or caused to be made a series of
    materially false or misleading statements about Gile-
    ad’s sales, business, product marketing and promo-
    tion, prospects, operations and financial results.
    These material misstatements had the cause and
             IN RE GILEAD SCIENCES SECURITIES LITIGATION     10331
       effect of creating in the market an unrealistically
       positive assessment of Gilead . . . thus causing the
       Company’s publicly traded securities to be overval-
       ued and artificially inflated at all relevant times.

II.    The District Court’s Decision

   The district court dismissed the complaint with prejudice.
Based on the Investors’ allegations and judicially-noticed
documents that had been referenced in the complaint, the
court concluded that the Investors had failed to adequately
plead loss causation as that requirement was articulated in
Dura Pharmaceuticals, Inc. v. Broudo, 

(2005).

     Specifically, the district court found the complaint failed to

       connect the following chain of events . . . : 1) that
       [Gilead’s and the Officers’] alleged failure to dis-
       close the off-label marketing scheme caused a mate-
       rial increase in sales; 2) that practitioners materially
       decreased their demand for Viread due to the publi-
       cation of the FDA Warning Letter; and most impor-
       tantly, 3) that the alleged decrease in sales due to the
       FDA letter proximately caused Gilead’s stock to
       decrease three months later[.]

   The district court rested its decision exclusively on loss
causation, and did not consider whether the Investors suffi-
ciently alleged falsity or scienter.

                          DISCUSSION

I.    Standards of Review

   “We review de novo the district court’s dismissal of a com-
plaint for failure to state a claim under Federal Rule of Civil
Procedure 12(b)(6). On review, we accept the plaintiffs’ alle-
gations as true and construe them in the light most favorable
10332      IN RE GILEAD SCIENCES SECURITIES LITIGATION
to plaintiffs.” Gompper v. VISX, Inc., 

, 895 (9th
Cir. 2002) (citation omitted). “The court need not, however,
accept as true allegations that contradict matters properly sub-
ject to judicial notice or by exhibit. Nor is the court required
to accept as true allegations that are merely conclusory,
unwarranted deductions of fact, or unreasonable inferences.”
Sprewell v. Golden State Warriors, 

, 988 (9th
Cir. 2001) (citation omitted), amended on other grounds, 

(9th Cir. 2001). The complaint is properly dis-
missed if it fails to “plead ‘enough facts to state a claim to
relief that is plausible on its face.’ ” Weber v. Dep’t of Veter-
ans Affairs, 

, 1065 (9th Cir. 2008) (quoting Bell
Atl. Corp. v. Twombly, 

, 1974 (2007)).

II.   Applicable law

   [1] Section 10(b) of the Securities Exchange Act of 1934
makes it unlawful “[t]o use or employ, in connection with the
purchase or sale of any security . . . any manipulative or
deceptive device or contrivance in contravention of such rules
and regulations as the Commission may prescribe.” 15 U.S.C.
§ 78j(b). Pursuant to this section, the Securities and Exchange
Commission promulgated Rule 10b-5, which makes it unlaw-
ful:

      (a) To employ any device, scheme, or artifice to
      defraud,

      (b) To make any untrue statement of a material fact
      or to omit to state a material fact necessary in order
      to make the statements made, in the light of the cir-
      cumstances under which they were made, not mis-
      leading, or

      (c) To engage in any act, practice, or course of busi-
      ness which operates or would operate as a fraud or
      deceit upon any person, in connection with the pur-
      chase or sale of any security.
           IN RE GILEAD SCIENCES SECURITIES LITIGATION     10333
17 C.F.R. § 240.10b-5.

   [2] We have identified five basic elements of a Rule 10b-5
claim: “(1) a material misrepresentation or omission of fact,
(2) scienter, (3) a connection with the purchase or sale of a
security, (4) transaction and loss causation, and (5) economic
loss.” In re Daou Sys., Inc., 

, 1014 (9th Cir.
2005) (citing Dura 

).

   Because the district court addressed only loss causation
under Rule 10b-5, we will limit our consideration to that
issue, “following the general rule [that] a federal appellate
court does not consider an issue not passed upon below.” Mil-
ler v. Thane Int’l, Inc., 

, 892 (9th Cir. 2008)
(alteration in original; internal quotation marks omitted). A
plaintiff bears the burden of proving that a defendant’s
alleged unlawful act “caused the loss for which the plaintiff
seeks to recover damages.” 15 U.S.C. § 78u-4(b)(4). To estab-
lish loss causation, “the plaintiff must demonstrate a causal
connection between the deceptive acts that form the basis for
the claim of securities fraud and the injury suffered by the
plaintiff.” 

. The misrepresentation
need not be the sole reason for the decline in value of the
securities, but it must be a “ ‘substantial cause.’ ” 

v. Koger Props., Inc., 

, 1447 n.5 (11th
Cir. 1997)).

   Rule 9(b) of Civil Procedure provides: “In alleging fraud
. . . a party must state with particularity the circumstances
constituting fraud . . . .” Gilead and the Officers contend that
the Investors’ loss causation arguments should be subject to
this heightened pleading requirement, although they recognize
that the Supreme Court has not decided the issue. See Dura

. The Investors argue that Rule
8(a)(2)’s “short and plain statement” requirement should con-
trol loss causation pleading.

  We need not resolve this issue today. Rule 9(b) imposes the
heightened requirement so that the fraud-action defendant
10334      IN RE GILEAD SCIENCES SECURITIES LITIGATION
“can prepare an adequate answer from the allegations.” Odom
v. Microsoft Corp., 

, 553 (9th Cir. 2007) (inter-
nal quotation marks omitted). As we explain below, the Inves-
tors’ complaint offers “sufficient detail to give defendants
ample notice of [their] loss causation theory, and to give us
some assurance that the theory has a basis in fact.” Berson v.
Applied Signal Tech., Inc., 

, 989-90 (9th Cir.
2008). Therefore, under either Rule 8 or Rule 9, the Investors
have sufficiently pleaded loss causation.

III.    The Sufficiency of the Complaint

   The district court identified Dura Pharmaceuticals as the
authority that doomed the Investors’ complaint. Dura featured
plaintiffs who alleged that they “paid artificially inflated
prices” for Dura’s securities and “suffered damages thereby.”

(alterations, emphasis, and quota-
tion marks omitted). The court below had held that loss causa-
tion was established merely by demonstrating that share
prices on the date of purchase were inflated. Broudo v. Dura
Pharms., Inc., 

, 938 (9th Cir. 2003).

  [3] The Supreme Court reversed, and held that an inflated
purchase price alone is not enough to establish loss causation.

. More is required of plaintiffs—
particular allegations as to “what the relevant economic loss
might be,” and “what the causal connection might be”
between the fraud alleged and the economic losses actually
suffered. 

   [4] The complaint in this case is meaningfully different
from that in Dura Pharmaceuticals. The Investors here iden-
tify a specific economic loss: the drop in value on October 29,
2003, that followed the October 28 press release. They also
allege that this loss was caused by Gilead’s misrepresenta-
tions. They provide abundant details of Gilead’s off-label
marketing, and they assert that this led to higher demand for
            IN RE GILEAD SCIENCES SECURITIES LITIGATION           10335
Viread, which in turn inflated Gilead’s stock price.6 As sum-
marized in the complaint’s introduction,

      [T]he market was not told that off-label marketing
      was the cornerstone of demand. This mistaken
      impression of demand led to, among other things,
      wholesaler overstocking in reaction to an anticipated
      price increase. When the truth about [Gilead’s and
      the Officers’] off-label marketing was disclosed,
      however, [they] could no longer maintain the sales
      growth levels that investors had come to expect, and
      Gilead’s stock price dropped accordingly.

   Assuming, then, that the Investors’ theory is sound and that
they can prove all that they allege, the district court erred by
holding that Dura Pharmaceuticals compelled dismissal of
this action.

  The dismissal order below, though, suggests that the district
court was unwilling to make these assumptions. The district
court found that the complaint contained “too many logical
and factual gaps.”

   [5] Based on our own review, we find the complaint suffi-
ciently alleges a causal relationship between (1) the increase
in sales resulting from the off-label marketing, (2) the Warn-
ing Letter’s effect on Viread orders, and (3) the Warning Let-
ter’s effect on Gilead’s stock price.

   Perhaps what truly motivated the dismissal was the district
court’s incredulity. The court expressly identified two allega-
tions it was unwilling to accept. First, it could not make “the
unreasonable inference that a public revelation on August 8
  6
    The complaint includes one concrete example of how Gilead’s stock
price was directly inflated by Viread’s sales performance: the 13.4% rise
in share value triggered by Gilead’s positive statements about demand for
Viread on July 14, 2003, the first day of the class period.
10336      IN RE GILEAD SCIENCES SECURITIES LITIGATION
caused a price drop three months later on October 28.” Order
Granting Defs.’ Mot. to Dismiss at 11. Second, with respect
to the Warning Letter’s impact on Viread sales, the court
found “a slowing increase in demand, alone, too speculative
to adequately demonstrate loss causation.” 

n.10.

   [6] As an initial matter, we note that a district court ruling
on a motion to dismiss is not sitting as a trier of fact. It is true
that the court need not accept as true conclusory allegations,
nor make unwarranted deductions or unreasonable inferences.

. But so long as the plaintiff alleges
facts to support a theory that is not facially implausible, the
court’s skepticism is best reserved for later stages of the pro-
ceedings when the plaintiff’s case can be rejected on evidenti-
ary grounds. “[A] well-pleaded complaint may proceed even
if it strikes a savvy judge that actual proof of those facts is
improbable, and that a recovery is very remote and unlikely.”
Bell Atl. Corp. v. Twombly, 

, 1965 (2007)
(internal quotation marks omitted).

   [7] There is no exception to this rule for the element of loss
causation. The Third Circuit has stated that “loss causation
becomes most critical at the proof stage,” and has cited schol-
arly authority stating that it is normally inappropriate to rule
on loss causation at the pleading stage. McCabe v. Ernst &
Young, LLP, 

, 427 n.4 (3rd Cir. 2007) (internal
quotation marks omitted). Similarly, the Second Circuit has
held that loss causation “is a matter of proof at trial and not
to be decided on a Rule 12(b)(6) motion to dismiss.” Emer-
gent Capital Inv. Mgmt., LLC. v. Stonepath Group, Inc., 

, 197 (2d Cir. 2003). But see Lentell v. Merrill Lynch
& Co., 

, 172-77 (2d Cir. 2005) (failure to plead
any facts supporting loss causation warranted 12(b)(6) dis-
missal of complaint).

   [8] We agree. So long as the complaint alleges facts that,
if taken as true, plausibly establish loss causation, a Rule
12(b)(6) dismissal is inappropriate. This is not “a probability
           IN RE GILEAD SCIENCES SECURITIES LITIGATION     10337
requirement . . . it simply calls for enough fact to raise a rea-
sonable expectation that discovery will reveal evidence of”
loss causation. Bell 

.

   The district court’s concern about the elapse of time
between the public issuance of the Warning Letter and the
drop in price recalls our holding in No. 84 Employer-Teamster
Joint Council Pension Trust Fund v. America West Holding
Corp., 

(9th Cir. 2003) (internal quotation marks
omitted). There, a Rule 10b-5 defendant argued that its
alleged misrepresentations were per se immaterial because the
injurious drop in stock price took place more than one and a
half months after the market learned the truth about the mis-
representations. 

We rejected “a bright-line rule
requiring an immediate market reaction” because “[t]he mar-
ket is subject to distortions that prevent the ideal of a free and
open public market from occurring.” 

marks omitted). Instead, we held that courts must engage in
a “fact-specific inquiry.” 

marks omit-
ted).

   [9] We believe that America West’s discussion of material-
ity applies with equal force to the loss causation requirement.
A limited temporal gap between the time a misrepresentation
is publicly revealed and the subsequent decline in stock value
does not render a plaintiff’s theory of loss causation per se
implausible.

   [10] Our review of the Investors’ complaint convinces us
that the October drop in stock price was plausibly caused by
the Warning Letter. Importantly, the drop occurred immedi-
ately after Gilead disclosed less-than-expected revenues
resulting from the reduction in wholesalers’ Viread invento-
ries, which analysts ascribed to lower end-user demand. That
lower end-user demand, in turn, is expressly alleged to have
been caused by the Warning Letter. In this light, the market
did react immediately to the corrective disclosure—the Octo-
ber 28 press release. The Warning Letter, which discussed
10338     IN RE GILEAD SCIENCES SECURITIES LITIGATION
only two instances of off-label marketing, would not neces-
sarily trigger a market reaction because it did not contain
enough information to significantly undermine Gilead’s July
2003 pronouncements concerning demand for Viread. It is not
unreasonable that physicians—the targets of the off-label
marketing—would respond to the Warning Letter while the
public failed to appreciate its significance.

   [11] The district court also erroneously concluded that a
slowing increase in demand is too speculative to establish loss
causation. Had the Investors alleged that the Warning Letter
eliminated all sales resulting from off-label marketing, it
would be very unlikely that demand would continue to
increase, since the complaint asserts that 75% to 95% of sales
were caused by off-label marketing. But they do not allege
that, and we see no reason why the court cannot proceed to
the evidentiary stages to determine the extent of the Warning
Letter’s impact on the growth of demand for Viread.

   [12] The complaint specifically alleges that physicians
were less eager to prescribe Viread, and competitors used the
Warning Letter to lure Viread customers to other drugs. This
is “enough fact to raise a reasonable expectation that discov-
ery will reveal evidence”—or the lack thereof—of the Warn-
ing Letter’s effect on demand. Bell 

.

                      CONCLUSION

   For the foregoing reasons, the district court improperly
granted Gilead’s and the Officers’ Rule 12(b)(6) motion. The
Investors have sufficiently alleged loss causation and eco-
nomic loss. We leave it to the district court to determine
whether they have sufficiently alleged the other elements of
their claims.

  REVERSED and REMANDED.