              United States Court of Appeals
                         For the First Circuit

No. 12-1750

    BRICKLAYERS AND TROWEL TRADES INTERNATIONAL PENSION FUND,

                         Plaintiff, Appellant,


  JAMES UPHOFF; GOODMAN FAMILY TRUST; MALKA BIRNBAUM, on behalf
    of herself and all others similarly situated; NEIL MCCARTY;
   RODNEY W. NARBESKY, individually and on behalf of all others
                        similarly situated,

                              Plaintiffs,

                                   v.

 CREDIT SUISSE SECURITIES (USA) LLC; CREDIT SUISSE (USA), INC.;
 JAMIE KIGGEN; FRANK P. QUATTRONE; LAURA MARTIN; ELLIOT ROGERS,

                         Defendants, Appellees.


              APPEAL FROM THE UNITED STATES DISTRICT COURT

                   FOR THE DISTRICT OF MASSACHUSETTS

            [Hon. Nathaniel M. Gorton, U.S. District Judge]


                                 Before

                         Howard, Circuit Judge,
                       Souter,* Associate Justice
                     and Torresen,** District Judge.


     Frederic S. Fox, with whom Kaplan Fox & Kilsheimer LLP and
Shapiro Haber & Urmy LLP were on brief, for appellant.


     *
      Hon. David H. Souter, Associate Justice (Ret.) of the Supreme
Court of the United States, sitting by designation.
     **
          Of the District of Maine, sitting by designation.
     Lawrence Portnoy, with whom Daniel J. Schwartz, Jonathan K.
Chang, Dharma Betancourt Frederick, Davis Polk & Wardwell LLP,
Robert Buhlman, Siobhan E. Mee, Amanda V. Muller, and Bingham
McCutchen LLP were on brief, for appellees.



                          May 14, 2014
             HOWARD, Circuit Judge.        Alleging violations of Sections

10(b) and 20(a) of the Securities Exchange Act and of SEC Rule 10b-

5, the appellant pension fund and other America Online ("AOL")

shareholders brought this class action against Credit Suisse First

Boston ("CSFB"), former CSFB analysts Jamie Kiggen and Laura

Martin, and other related defendants.             The shareholders claim that

CSFB fraudulently withheld relevant information from the market in

its   reporting      on   the   AOL-Time    Warner    merger,    and    that   the

shareholders purchased stock in the new company at prices that were

artificially inflated as a result of the defendants' purposeful

omissions.     This appeal concerns the admissibility of the opinion

of the shareholders' expert Dr. Scott D. Hakala, whose testimony

the district court precluded for lack of reliability.                  We find no

abuse of discretion in that decision.                We also agree with the

district     court    that,     without     the    expert's     testimony,     the

shareholders are unable to establish loss causation.                      Summary

judgment was therefore properly awarded to the defendants.

                                 I. Background

             A.       Facts

             On January 11, 2001, Time Warner Inc. and AOL merged into

a single media and technology company (hereinafter referred to as

"AOL").    This marriage of "old" and "new" media received extensive

coverage from both the press and the financial industry.                 CSFB was

among the many financial firms reporting on AOL's business and


                                      -3-
forecasting its outlook for the future.            Kiggen and Martin headed

CSFB's   AOL   coverage   beginning    the   day    after   the   merger   and

continuing for about a year, through January 2002, when CSFB ceased

covering AOL (Kiggen retired in January 2002; Martin had left CSFB

a few months earlier).     During the coverage period, CSFB published

the results of its research in regular reports.             These contained,

in addition to observations about AOL, a buy or sell recommendation

and a price target, which was a prediction of AOL's stock price

twelve months hence.      CSFB issued thirty-five such reports during

this period, and each such report recommended buying AOL stock.

CSFB initially targeted AOL's future stock price at $80, but

revised it downwardly to $75 one month later in February 2001, and

then to $45 in September 2001.        Nine months later, AOL's stock was

trading at $11 per share.

           The   shareholders     allege     that      Kiggen     and   Martin

misrepresented their true opinions in these reports, in order to

maintain a good relationship with AOL. The shareholders' theory is

that AOL had the potential to generate significant investment

banking revenue for CSFB, and Kiggen and Martin overstated AOL's

financial strength in the hopes of winning this future business

(CSFB did in fact assist AOL in managing a bond deal purportedly

generating between $750,000 and $820,000 in fees for CSFB).                In a

series of internal emails among AOL team members, Kiggen and Martin

expressed doubts about their projections for AOL, yet decided not


                                   -4-
to   lower     their   estimates      for     AOL's     future       performance

notwithstanding these concerns.           Moreover, they regularly showed

their projections to AOL and revised them based on AOL's reactions.

Even as advertising revenue, a key factor in AOL's success,

declined throughout the industry, CSFB reports continued to predict

AOL's ability to rise above the general slowdown.

             In addition, the shareholders allege two instances in

which CSFB1 received non-public, material information about AOL

that CSFB did not disclose in its coverage of the company.                  On July

10 and 11, 2001, Anthony Lorenzo, a junior CSFB analyst not

assigned to cover AOL, emailed to Kiggen information about AOL

layoffs.      Citing   an   unnamed   source,    Lorenzo      wrote    that    AOL

"apparently . . . had some layoffs" that "were medium in terms of

severity and will not be announced publicly." The parties disagree

over the import of this tip.           The shareholders claim that the

information    pertained    to   layoffs    of   "up    to   1,000    employees"

subsequently reported in The Wall Street Journal and The Washington

Post on August 13 and 14, 2001.           CSFB counters that this unnamed

source    (later   identified    as   a     low-level    employee      in    AOL's

Interactive Marketing Group) was referring only to a small number

of layoffs that occurred within the Interactive Marketing Group on

July 10, 2001, as reported in The Washington Post the next day.



     1
          At times, we refer to the defendants, collectively, as
"CSFB".

                                      -5-
            Lorenzo's emails also mentioned "that AOL was under

investigation and has suspended some employees for inappropriate

accounting activities -- some deals booked inappropriately inflated

revenue."     CSFB did not disclose this information in any of its

reports; it was eventually reported by The Washington Post in a

July   2002      article   disclosing    that     AOL   had     engaged    in

"unconventional"     advertising   deals   that    might      have   inflated

revenue.      On July 24, 2002, AOL acknowledged that the SEC was

investigating its accounting practices, but denied any wrongdoing.

            B.      Procedural History

            On the basis of these alleged material misstatements and

omissions -- overstating AOL's financial strength, not disclosing

reports of medium-severity layoffs, and not disclosing reports of

unconventional accounting -- the shareholders brought suit in

December 2005 against Kiggen, Martin, and CSFB under Section 10(b)

of the Exchange Act, 15 U.S.C. § 78j(b), and under SEC Rule 10b-5.

The complaint also alleged that CSFB, Credit Suisse First Boston

(USA) Inc. (CSFB's parent company), and CSFB executives Frank

Quattrone and Elliot Rogers violated Section 20(a) of the Exchange

Act, 15 U.S.C. § 78t(a), by failing to exercise control over their

employees' alleged misstatements and omissions.

            In due course, the defendants sought summary judgment.

At the hearing occasioned by that motion, the shareholders and the

defendants each presented expert testimony to show the effect, or


                                   -6-
lack thereof, of CSFB's omissions on AOL stock prices.          The

shareholders retained Dr. Hakala, while CSFB employed Dr. René M.

Stulz.   Each side subsequently moved to exclude the other's expert

opinion under Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579,

597 (1993) ("[T]he Rules of Evidence--especially Rule 702--[]assign

to the trial judge the task of ensuring that an expert's testimony

both rests on a reliable foundation and is relevant to the task at

hand.").    In due course, the court held a Daubert hearing to

determine the admissibility of the proffered expert testimony on

loss causation.

           C.      Event Studies and Expert Testimony

           Loss causation is among the six elements of a private

cause of action for securities fraud; the other five are:          a

material misrepresentation or omission, scienter, a connection with

the purchase or sale of a security, reliance, and economic loss.

Dura Pharm., Inc. v. Broudo, 544 U.S. 336, 341-42 (2005). To prove

loss causation, a plaintiff "must show 'a sufficient connection

between [the fraudulent conduct] and the losses suffered . . . .'"

In re Omnicon Grp., Inc. Sec. Litig., 597 F.3d 501, 510 (2d Cir.

2010) (quoting Lattanzio v. Deloitte & Touche LLP, 476 F.3d 147,

157 (2d Cir. 2007)) (alterations in original). In other words, the

stock market must have reacted to the subsequent disclosure of the

misconduct and not to a "tangle of [other] factors."    Dura Pharm.,

544 U.S. at 343.


                                 -7-
          The usual -- it is fair to say "preferred" -- method of

proving loss causation in a securities fraud case is through an

event study, in which an expert determines the extent to which the

changes in the price of a security result from events such as

disclosure of negative information about a company, and the extent

to which those changes result from other factors.2      First, the

expert selects the period in which the event could have affected

the market price.3   The expert then attempts to determine the

effect on the share price of general market conditions, as opposed

to company-specific events, using a multiple regression analysis,

a statistical means for explaining the relationship between two or

more variables.   1 David L. Faigman et al., Modern Scientific

Evidence; The Law and Science of Expert Testimony 430 (2012).

Thus, for any given day, the expert predicts the company's share

price based on the market trends on that particular day.       The

expert then compares this predicted return with the actual return

in the event window in order to determine the probability that an

abnormal return of that magnitude could have occurred by chance.


     2
        For additional information about event studies in
litigation, see Sanjai Bhagat & Roberta Romano, Event Studies and
the Law: Part I: Technique and Corporate Litigation, 4 Am. L. &
Econ. Rev. 141 (2002), and Michael J. Kaufman & John M. Wunderlich,
Regressing: The Troubling Dispositive Role of Event Studies in
Securities Fraud Litigation, 15 Stan. J. L. Bus. & Fin. 183, 186
(2009).
     3
       "Stock price," "share price," "market price," "closing
price," and "return" are all used interchangeably throughout this
opinion.

                               -8-
If this probability is small enough, the expert can reject the

hypothesis that normal market fluctuations, as opposed to company-

specific events, can explain the movement in the share price.

             Central to multiple regression analyses are variables,

which, as the term implies, can have two or more possible values.

Id.   n.1.   Multiple regression includes a variable to be explained

(the dependent variable) and explanatory (or independent) variables

that have the potential to be associated with changes to the

dependent variable. Id. at 430. ("[A] multiple regression analysis

might estimate the effect of the number of years of work on salary.

Salary would be the dependent variable to be explained; years of

experience would be the explanatory variable."). The third type of

variable at issue in this case is a dummy variable,    which is also

known as a "binary variable" because it only has two possible

values, such as gender, or, as in this case, the existence or non-

existence of company-specific events.4    By assigning the variable


      4
       An opinion from the District of New Jersey provides a
succinct example of the use of a dummy variable:

      [S]uppose   you   are  investigating    [United   States]
      consumption behavior with time series data for the period
      1930 to 1950. You would expect that consumption behavior
      would have been significantly different during the years
      of World War II than it was before and after the war. To
      take this effect into account, you can create an
      artificial variable that will take the value 1 during
      each of the war years and the value 0 during each of the
      other years.

Animal Sci. Prods., Inc. v. China Nat'l Metals & Minerals Imp. &
Exp. Corp., 702 F. Supp. 2d 320, 358 n.44 (D.N.J. 2010).

                                  -9-
a value of zero or one in the mathematical formulae used in the

analysis,   the   dummy   variable    becomes   mutually   exclusive   with

respect to any explanatory variables, unable to exist or affect the

outcome simultaneously.       Thus, by using a dummy variable, the

projected various outcomes can reveal which explanatory variables

affect the dependent variable.

            D.     Dr. Hakala's Event Study

            Such is the basic structure of an event study.         In its

motion to exclude Dr. Hakala's testimony, CSFB alleged that his

methodology included techniques that did not meet the standards of

reliability articulated in Daubert. It challenged four elements of

Dr. Hakala's study.

                   1.     Selection of Event Dates

            The first alleged flaw in Dr. Hakala's analysis was his

selection of event dates.     CSFB claimed that Dr. Hakala failed to

conform to event study methodology by selecting his event dates

after running his regression analysis.          As noted previously, the

first step of an event study is identifying the relevant dates that

are the focus of the study.     CSFB argued that Dr. Hakala reversed

the steps in this process, first conducting a regression analysis,

and then, after identifying fifty-seven dates with statistically

significant abnormal returns, using them as the relevant dates for

his event study.




                                     -10-
            According to CSFB, this results-driven approach produced

event dates that had "little relationship with the allegations or

facts in this case and ma[de] no sense even under [Dr. Hakala's]

own   definition      of    'relevance.'"          For     instance,    Dr.      Hakala

attributed some abnormal market increases in AOL stock prices to

the defendants on days when CSFB released no reports about AOL --

often when it was no longer reporting about AOL.                    Dr. Hakala also

characterized several of the dates in his study as corrective,

despite     the    fact    that    the    complaint      had      labeled   them     as

inflationary.5      On one event date, the abnormal market return was

negative, yet Dr. Hakala classified the date as inflationary.

Finally, Dr. Hakala often identified dates as corrective when no

negative    information      entered      the    market,    and    other    dates   as

inflationary when no positive information entered the market.

                      2.     Overuse of Dummy Variables

            CSFB    also    asserted      that    Dr.    Hakala's    use    of    dummy

variables not only overstated the baseline stability of AOL's stock

prices, but also failed to satisfy the Daubert requirement of

reproducibility.      The goal of a regression analysis is to create a

baseline    against       which   the    market   return     on    event    dates   is

measured.     Through the use of dummy variables, the event dates



      5
        An inflationary date occurred when misinformation or
omissions inflated AOL's stock price. A corrective date occurred
when truthful information caused AOL's stock price to return to its
normal levels.

                                         -11-
themselves are excluded from, or "dummied out" of, the regression

analysis to indicate the presence or absence of some event.               This

is designed to prevent the event days themselves from distorting

the baseline.         Dr. Hakala, in addition to dummying out relevant

event dates, dummied out all dates containing material news about

AOL.6       He chose this approach to control for days when AOL's stock

price might have fluctuated due to the release of information that

was, for purposes of this litigation, irrelevant. He believed that

these material news dates could improperly influence the baseline

regression, and cited other financial economists who endorse this

methodology.       Using this approach, Dr. Hakala dummied out 211 out

of 388 days in the study period -- 54% of the total number of days.

CSFB argued that Dr. Hakala's approach went too far, creating an

unrealistically stable baseline and thereby ensuring that all

relevant event dates would appear more unusual than they really

were.

               CSFB   also   attacked   Dr.    Hakala's   dummy   selection   as

arbitrary.       Dr. Hakala performed three event studies relating to

the America Online-Time Warner merger.             Although he used the same




        6
       The terms "relevant event dates" and "material news dates,"
though similar, are distinct. Relevant event dates are the fifty-
seven dates that are the focus of Dr. Hakala's event study.
Material news dates refer to the additional one hundred fifty-four
dates Dr. Hakala dummied out of his event study because they
contained material news.

                                        -12-
criteria to select the material dates each time,7 he dummied out

more material dates in each subsequent study. CSFB argued that his

selection criteria were so vague that two economists would be apt

to pick vastly different numbers of material dates given the same

instructions.     Thus, CSFB argued, Dr. Hakala's methodology cannot

be replicated.        See Daubert, 509 U.S. at 593 ("Ordinarily, a key

question   to    be    answered   in   determining    whether   a   theory   or

technique is scientific knowledge that will assist the trier of

fact will be whether it can be (and has been) tested.").             The proof

of this flaw, according to the defendants, was the fact that even

Dr. Hakala could not select the same number of material news dates

in three separate event studies.

                      3.    Previously Disclosed Information

              In Basic Inc. v. Levinson, 485 U.S. 224 (1988), the

Supreme Court held that a plaintiff in a securities fraud suit need

not   prove    individual    reliance    on   the    defendants'    fraudulent

statements when purchasing company stock.             Id. at 247.    Instead,

courts will presume reliance as long as the company's shares trade

in an efficient market, that is, one which incorporates all public



      7
       Dr. Hakala's criteria came from "the NASDAQ guidelines as
recognized by the SEC." See Self-Regulatory Organizations; Notice
of Filing of Proposed Rule Change by the National Association of
Securities Dealers, Inc. Relating to Issuer Disclosure of Material
Information, 67 F.R. 51,306 (Jul. 31, 2002).     He also included
"third party news and reports, and analysts' reports to that list
consistent with the academic studies."


                                       -13-
statements     about   the   company       --   including    the    defendants'

fraudulent statements -- into its share price.              Id.     "An investor

who buys or sells stock at the price set by the market does so in

reliance on the integrity of that price."               Id.        Consequently,

investors must also implicitly rely on the integrity of the

information    affecting     the   stock    price.    Investors       who   avail

themselves of the fraud-on-the-market theory recognized in Basic,

however, must be consistent.          If it is assumed that the market

reacts to the fraud, it must also be assumed that it reacts to the

truth.   Accordingly, once a misstatement or corrective disclosure

is publicly known in an efficient market, courts will assume that

the stock price reacts immediately, and any claim that an event

moved the stock price when the event was not actually a new

disclosure will necessarily fail.8

           CSFB argued that Dr. Hakala's event study included some

"new disclosures" that were not in fact new to the market.                  CSFB

pointed to several instances in Dr. Hakala's event study when he

attributed the rise or fall of AOL's stock price to the disclosure

of   "stale"    information.        Consequently,     CSFB    averred,      this

information could not form the basis of a proper event date, and




     8
       A case pending before the Supreme Court has raised the issue
of the continuing viability of the fraud-on-the-market theory. See
Halliburton Co. v. Erica P. John Fund, Inc., No. 13-317 (U.S.
argued March 5, 2014).

                                     -14-
Dr. Hakala's rejection of the efficient market hypothesis rendered

his study inadmissible.

          4.       Failure to Control for Confounding Factors

          The purpose of an event study, as noted, is to isolate

the impact of an alleged misstatement, omission, or disclosure on

the stock price.     A recurring problem in event studies is the

presence of "confounding factors" -- news stories, statements, or

events that coincide with relevant event dates and that themselves

potentially affect the company's stock price.     CSFB claimed that

Dr. Hakala made no attempt to control for the many confounding news

stories that emerged at the same time as CSFB reports and other

relevant events, and therefore that his event study did not show

that CSFB's statements, as opposed to some other news story, moved

the stock price on any given day.

          E.       The District Court's Opinion

          In January 2012, the district court issued an order

precluding Dr. Hakala's testimony, relying on the four factors

argued in CSFB's motion to preclude.       While it gave specific

examples for each factor, the court explained that these were

illustrative of pervasive problems.

          With respect to the event date selection, the district

court determined that

     "[r]ather than study the market's reaction to the
     misrepresentations alleged in the complaint, Dr. Hakala
     cherry-picked unusually volatile days and made them the
     focus of his study.     If the stock price increased

                                -15-
      sharply, he attributed it to the defendants (even if no
      CSFB reports were released on that day). If the stock
      price decreased sharply, he called it a corrective
      disclosure (even if the news released was positive). The
      Court concludes . . . that, quite simply, Dr. Hakala's
      theory does not match the facts.

Bricklayers & Trowel Trades Int'l Pension Fund v. Credit Suisse

First Boston, 853 F. Supp. 2d 181, 188 (D. Mass. 2012) (citations

omitted)   (internal     quotation      marks     and    alterations     omitted),

reconsideration denied, published in 853 F. Supp. 2d 181, 195 (D.

Mass. May 17, 2012).

           Next, and with little independent analysis, the district

court followed the reasoning of two other district courts in

concluding that Dr. Hakala's use of dummy variables was also

unreliable.     See In re Northfield Labs., Inc. Sec. Litig., 267

F.R.D. 536, 548 (N.D. Ill. 2010); In re Xcelera.com Sec. Litig.,

No. 00-11649-RWZ, 2008 WL 7084626, at *1 (D. Mass. Apr. 25, 2008).

In those cases, courts had criticized the high percentage of

dummied-out    dates    in   Dr.     Hakala's    studies,     finding    that   the

practice artificially stabilized the baseline regression.                   Here,

the district court noted that Dr. Hakala had dummied out a higher

percentage of days in this study than in either of those cases.                 It

concluded that "[i]f those courts were correct in excluding his

event studies . . . , as this Court believes they were, it follows

a   fortiori   that    his   event    study     should   be   excluded    here."

Bricklayers, 853 F. Supp. 2d at 189.



                                       -16-
             The district court also found that Dr. Hakala's study

"repeatedly ignores the efficient market principle" by attributing

price fluctuations to previously disclosed information.                Id.    The

shareholders' attempt to "presume an efficient market to prove

reliance and an inefficient market to prove loss causation,"

according to the district court, was tantamount to "hav[ing] their

cake and eat[ing] it too."        Id. at 190.

             Finally, the district court rejected Dr. Hakala's attempt

to disaggregate confounding information on the event dates.                    It

acknowledged that AOL received near uninterrupted coverage during

the Class Period, making Dr. Hakala's task difficult.                   But it

concluded that Dr. Hakala did not use an accepted means for

separating the impact of the relevant event from the impact of

confounding information.         As an example of one method that Dr.

Hakala could have used, the district court discussed intra-day

trading analysis.      This analysis requires tracking the stock price

throughout    the    day   to   see   whether   its   daily    highs   or    lows

correspond with the relevant event, or with the release of some

other information.         Dr. Hakala did not do this.            Instead, he

"either attributed a rough proportion of the movement to each

report or blamed it all on the defendants."                Id. at 191.        The

district     court     considered      this     approach      unreliable      and

unscientific.




                                      -17-
          The court ultimately concluded that Dr. Hakala's event

study lacked sufficient reliability to be presented to a jury.    It

indicated that "[h]ad Dr. Hakala's event study suffered from only

one of the four methodological defects identified by this Court, or

suffered from those flaws jointly but to a lesser degree, today's

ruling might have been different," id. at 191, but, given the

extent of Dr. Hakala's errors, preclusion was necessary.

          The district court awarded summary judgment to CSFB sua

sponte, deciding that Dr. Hakala's event study, "even if it were

admitted," did not raise a triable issue of loss causation.9     Id.

at 191-92.     The district court's reasoning largely restated the

problems that persuaded it to preclude Dr. Hakala's event study.

             After their motion for reconsideration was denied, the

shareholders appealed both the preclusion of Dr. Hakala's event

study and the grant of summary judgment.

                            II. Analysis

          A.       Expert Testimony

          We review a district court's decision to exclude an

expert witness's testimony for abuse of discretion.     Milward v.

Acuity Specialty Prods. Grp., Inc., 639 F.3d 11, 13 (1st Cir.

2011).   "This standard is not monolithic:     within it, embedded

findings of fact are reviewed for clear error, questions of law are


     9
       The defendants' original motion for summary judgment had
been denied earlier, subject to being revisited if the court
determined that Dr. Hakala's testimony should be excluded.

                                -18-
reviewed de novo, and judgment calls are subjected to classic

abuse-of-discretion review."        Ungar v. Palestine Liberation Org.,

599 F.3d 79, 83 (1st Cir. 2010).

            Since the Supreme Court's decision in Daubert, trial

judges have acted as gatekeepers of expert testimony, assessing it

for reliability before admitting it. See Milward, 639 F.3d at 14.

Expert    testimony   comes   in    many    different    forms,     but   certain

non-exclusive factors can assist a trial court in its task:                  "(1)

whether the theory or technique can be and has been tested; (2)

whether    the   technique    has   been    subject     to   peer   review    and

publication; (3) the technique's known or potential rate of error;

and (4) the level of the theory or technique's acceptance within

the relevant discipline." United States v. Mooney, 315 F.3d 54, 62

(1st Cir. 2002) (citing Daubert, 509 U.S. at 593-94). Moreover, an

expert's opinion must be relevant "not only in the sense that all

evidence must be relevant, but also in the incremental sense that

the expert's proposed opinion, if admitted, likely would assist the

trier of fact to understand or determine a fact in issue."

Ruiz-Troche v. Pepsi Cola of P.R. Bottling Co., 161 F.3d 77, 81

(1st Cir. 1998) (citations omitted).

            As the district court observed, no single factor is

dispositive in determining the admissibility of Dr. Hakala's expert

testimony. Consequently, we will address the four factors from the




                                     -19-
district court's opinion individually before analyzing the overall

admissibility of Dr. Hakala's testimony

                    1.     Selection of Event Dates

             The district court committed no abuse of discretion in

concluding that Dr. Hakala selected event dates based on unreliable

criteria.     Event selection should not be difficult to understand,

yet Dr. Hakala's event study leaves us guessing as to how he chose

the fifty-seven dates included in his study.            He certainly did not

rely on the shareholders' complaint.                Not only did Dr. Hakala

include many dates that bear no relationship to the allegations in

the complaint, in some instances he has turned the complaint on its

head, treating certain events as corrective when the complaint

labeled them inflationary.            This complete disconnect between the

event study and the complaint nullifies the usefulness of Dr.

Hakala's work; from all appearances, the event study is more

concerned simply with identifying abnormal market movement than in

supporting the shareholders' causation allegations. Thus, we agree

with the district court's negative assessment of Dr. Hakala's

selection of event dates.

             On appeal, the shareholders argue that the district court

could only arrive at this conclusion by rejecting Dr. Hakala's

testimony,    and   that    by   so    doing   it   interposed   itself      as   a

fact-finder.     It is true that a trial court should not "determine

which   of   several     competing     scientific    theories    has   the   best


                                       -20-
provenance."        Id. at 85.         If an expert has reached her conclusion

"in a scientifically sound and methodologically reliable fashion,"

id., the differences "should be tested by the adversarial process,"

Milward, 639 F.3d at 15.               Moreover, the court should not rely on

credibility     determinations           to    resolve   a     disagreement   between

experts.      See Seahorse Marine Supplies, Inc. v. P.R. Sun Oil Co.,

295    F.3d   68,    81   (1st    Cir.     2002)     ("The     ultimate   credibility

determination and the testimony's accorded weight are in the jury's

province.").

              Here, Dr. Hakala stated on several occasions that he

pre-selected relevant event dates without reference to the stock

price, yet the district court specifically found, to the contrary,

that Dr. Hakala had "cherry-picked unusually volatile days and made

them the focus of the study." Bricklayers, 853 F. Supp. 2d at 188.

The    shareholders       claim    that       the   district    court   impermissibly

discredited Dr. Hakala's testimony on this issue.                       This argument

misses the point.         The problem is not whether Dr. Hakala selected

his event dates with reference to AOL's stock price.                      The problem

is that the indisputably volatile dates that Dr. Hakala selected

were    often   unrelated         to    the     shareholders'     allegations,    and

therefore do not "help the trier of fact to understand the evidence

or to determine a fact in issue."                    Fed. R. Evid. 702(a).        The

district court focused on this deficiency, and not on the mechanics

of how Dr. Hakala selected these event dates. Consequently, we see


                                           -21-
no     reason   to     address    whether           the    district   court   made    an

impermissible credibility determination.

                       2.      Overuse of Dummy Variables

             We turn next to the district court's conclusion that Dr.

Hakala overused dummy variables, which, according to the court,

"artificially deflated the baseline volatility of AOL's stock price

during the Class Period."              Bricklayers, 853 F. Supp. 2d at 189.

While our review of the record lends some support to the district

court's assessment, there are countervailing factors suggesting

that Dr. Hakala's exclusion of various dates during the Class

Period affects only the weight, and not the admissibility, of his

event study.

             CSFB argued, and the district court agreed, that "Dr.

Hakala's event study uses a much higher percentage of dummy

variables       than    is     considered       acceptable       in   the     financial

econometric community."           Id. at 188.             We think, however, that in

arriving at this conclusion, the court may have given insufficient

weight to the shareholders' proffer.                       The shareholders offered

scholarship, see, e.g., Robert B. Thompson, II, et al., The

Influence of Estimation Period News Events on Standardized Market

Model Prediction, 63 Acc. Rev. 448, 466 (1988) ("[T]he distribution

of security returns during periods in which Wall Street Journal

news    is   released        appears    to    differ       systematically     from   the

distribution of non-release period returns.                      This 'news-release'


                                             -22-
effect can be incorporated in models of the returns generating

process by conditioning on news releases."), as well as expert

testimony     from   Dr.   M.   Laurentius    Marais10   that   supported   Dr.

Hakala's approach.

              CSFB has identified articles that describe event study

methodologies without mentioning the option of controlling for

material news.       See, e.g., A. Craig MacKinlay, Event Studies in

Economics and Finance, 35 J. Econ. Literature 13, 17-19 (describing

various market models for event studies without mentioning a news-

conditioned model, but noting that "[t]he use of other models is

dictated by data availability").              The shareholders, meanwhile,

point to academic event studies that do control for material news

dates using a definition of "material news" narrower than Dr.

Hakala's.     See, e.g., Richard Roll, R2, 43 J. Fin. 541, 558 (1988)

(selecting material news from the Dow-Jones news service and The

Wall Street Journal).

              Ultimately, Dr. Hakala's approach may not be inconsistent

with    the   methodology   or   goals   of    a   regression   analysis.    A

regression analysis seeks to isolate the effect that one variable

has on another.       Dr. Hakala's event study sought to isolate the

effect of the general market conditions on AOL's stock price.               He

believes that "material news dates" have the potential to distort



       10
        Dr. Marais submitted testimony rebutting                 Dr.   Stulz's
criticism of Dr. Hakala's use of dummy variables.

                                     -23-
this relationship, and therefore excludes them from his analysis.

Other market economists may disagree with the efficacy of this step

or with the way that he defines materiality, but it is hard to see

how it fails to follow the logic of regression studies.     Indeed,

CSFB's event study excludes certain dates for precisely the same

reason.   Nor do we consider the percentage of dummied-out dates

dispositive of the issue.   The district court was troubled by the

fact that Dr. Hakala excluded 211 of the 388 dates in the study

period.   Bricklayers, 853 F. Supp. 2d at 188.    That fact alone,

however, does not negate the reliability of his study.          The

remaining 177 dates provided enough data to conduct a robust

regression analysis.   As Dr. Marais (the shareholders' expert on

the issue of dummy variables) noted, the important factor is not

"the mechanistic and superficial percent of some universe of

observations" that Dr. Hakala dummied out, but the "valid technical

principles concerning the validity of the exercise."

          The district court noted two previous court opinions that

disapproved of Dr. Hakala's use of dummy variables.    We have held,

however, that "the question of admissibility must be tied to the

facts of a particular case." Milward, 639 F.3d at 14-15 (citations

omitted) (internal quotation marks omitted).     The importance of

that counsel is manifest here.   Based on the record before us, Dr.

Hakala's event studies in those two cases differed from this one in

at least one key respect:   in the other cases he dummied out dates


                                 -24-
on which "any news" about the company appeared.              Northfield Labs.,

267 F.R.D. at 548; see also Xcelera, 2008 WL 7084626, at *1.                   This

is not a frivolous distinction, and the district court in Xcelera

highlighted its importance:           "Although the academic literature

supports the use of dummy variables for events in which significant

company-specific     news    is   released,    no    peer-reviewed       journal

supports the view that dummy variables may be used on all dates on

which any company news appears." Xcelera, 2008 WL 7084626, at *1.

No one contends that Dr. Hakala dummied out every day in which AOL

appeared in a news story, yet that was precisely the problem in

Northfield    and   Xcelera.11       Given   that   Dr.    Hakala   employed     a

different methodology for this case, Northfield and Xcelera are of

limited value in assessing it.

             In Bazemore v. Friday, 478 U.S. 385, 400 (1986) The

Supreme   Court     observed     that,   "Normally,       failure   to    include

variables    will   affect     the   analysis'      probativeness,       not   its

admissibility."      Thus, while Dr. Hakala's use of dummy variables

may, as defendants contend, have artificially deflated the baseline

volatility of AOL's stock in his regression analysis, it may be a

dispute that should be resolved by the jury.



     11
        CSFB argues that Dr. Hakala employed the same "material
news" standard in his event studies in Northfield and Xcelera as he
did here. That may be true, but it does not address the fact that
the courts in those cases specifically found that Dr. Hakala
excluded any date containing company-specific news.        No such
finding exists in this case.

                                      -25-
          CSFB launches one more assault on Dr. Hakala's use of

dummy variables.     It contends that his methodology fails under

Daubert because it cannot be replicated.         Dr. Hakala has performed

three separate event studies related to the AOL merger, and each

time he has dummied out more material news dates than before.

Consequently, CSFB argues, his selection of material news dates is

arbitrary and could not be replicated by another economist. We are

not so sure.

          Daubert suggests that a key question in determining

whether a particular technique is scientific knowledge that will be

useful to a jury is "whether it can be (and has been) tested."

Daubert, 509 U.S. at 593.     There, the Court was encouraging trial

courts to limit expert testimony to falsifiable theories, meaning

those "capable of empirical test."         Id. (quoting Carl Hempel,

Philosophy of Natural Science 49 (1966)).           Testing a particular

theory will either reproduce consistent results, thus confirming

the theory, or inconsistent results, thus casting doubt on it.         In

this   case,   Dr.   Hakala   has    theorized     that,   given   certain

assumptions, AOL's stock experienced abnormal returns on fifty-

seven event dates.     One would test that theory by repeating his

event study under the same conditions that he did.         This would not

be a difficult task, since Dr. Hakala has provided all of the

necessary guidelines to recreate his event study.




                                    -26-
             Rather than put Dr. Hakala to the test, CSFB has simply

argued that Dr. Hakala's techniques are unreproducible because of

differences in the number of material news dates that he has

dummied out in successive event studies.                But CSFB here is not

comparing apples to apples. Only one of the three studies to which

they refer is at issue here.            One of the others was created in

support of class action certification; the other was in connection

with a different lawsuit.             That fact alone could be enough to

neuter CSFB’s argument and leave such matters as fodder for cross-

examination, not exclusion.

             Ultimately, both the number of dates Dr. Hakala excluded

from consideration and the methods he employed to select those

dates create close questions.            And while, as noted, appellant's

arguments raise credible questions, we need not resolve this

particular sub-issue because, as the district court concluded, the

other three bases for excluding Dr. Hakala's testimony are sound.

                      3.     Prior Disclosures

             We have described an efficient market for the purpose of

class action securities litigation as "one in which the market

price   of    the    stock    fully    reflects   all    publicly   available

information."       In re PolyMedica Corp. Sec. Litig., 432 F.3d 1, 14

(1st Cir. 2005).      We have also explained that the relevant inquiry

is whether the market is informationally efficient, id. at 16,

meaning that "all publicly available information is impounded in


                                       -27-
[the] price" rapidly after it is disseminated.       Id. at 14.      The

district court correctly applied this standard to Dr. Hakala's

event study.     Having established that AOL stocks traded in an

efficient market in order to obtain class certification, the

shareholders could not abandon that factual premise when proving

loss causation. Yet several of the relevant events in Dr. Hakala's

study are based on published references to information previously

disclosed that, under an efficient market theory, would have

already been incorporated into AOL's share price.     The lag between

the original disclosure and the event date ranged from one day to

roughly a month.    The majority of these disclosures occurred at

least a week before the event dates; thus, the event dates occurred

long after an efficient market would have processed the news.

          The shareholders respond that the event dates included

new information that was not contained in the original disclosures.

We conclude, however, that while the disclosures made on the event

dates did not merely parrot previously released information, they

did no more than to provide gloss on public information, and thus

permitted the district court to find that they would not have moved

AOL's share price in an efficient market.     See In re Omnicon Grp.,

597 F.3d at 512 (holding that the "negative characterization of

already-public   information"   does   not   constitute   a   corrective

disclosure of new information).   For instance, Dr. Hakala included

a February 2001 Lehman Brothers report on AOL.      While this report


                                -28-
downgraded its January 2001 buy or sell recommendation for AOL, it

based this downgrade on information that was known the previous

month.    That Lehman Brothers reconsidered its initial appraisal of

AOL’s business, or lost confidence in AOL from one month to the

next, does not demonstrate corrective information entering the

market.    See id. ("A negative journalistic characterization of

previously    disclosed   facts   does   not   constitute   a   corrective

disclosure of anything but the journalists' opinions.").               The

district court did not abuse its discretion in determining that

this recurring problem affected the admissibility of Dr. Hakala's

event study.

                   4.     Confounding Factors

            When proving loss causation in a securities fraud suit,

plaintiffs "bear[] the burden of showing that [their] losses were

attributable to the revelation of the fraud and not the myriad

other factors that affect a company's stock price." In re Williams

Sec. Litig., 558 F.3d 1130, 1137 (10th Cir. 2009); Dura, 544 U.S.

at 343 (holding that a plaintiff does not show loss causation if

the lower share price reflects "not the earlier misrepresentation,

but changed economic circumstances, changed investor expectations,

new industry-specific or firm-specific facts, conditions, or other

events, which taken separately or together account for some or all

of that lower price").      Thus, when conducting an event study, an




                                  -29-
expert must address confounding information that entered the market

on the event date.

             This case deals with a highly publicized merger that

captured the attention of the entire financial industry.                There is

no doubt that Dr. Hakala faced a "herculean task" in sorting

through the continuous flow of information about AOL. Bricklayers,

853 F. Supp. 2d at 190.       We agree with the district court, however,

that Dr. Hakala did not establish any reliable means of addressing

this problem.      Instead, he seemingly made a judgment call as to

confounding information without any methodological underpinning.

             In support of Dr. Hakala's treatment of confounding

factors,   the    shareholders       correctly   point   out     that   "even    a

statistical event study involves subjective elements." In re Xerox

Corp. Sec. Litig., 746 F. Supp. 2d 402, 412 (D. Conn. 2010)

(citations      omitted)      (internal   quotation      marks     omitted).

Nevertheless, a subjective analysis without any methodological

constraints does not satisfy the requirements of Daubert.                As the

district court noted, "[i]t would be just as scientific to submit

to the jurors evidence of defendants' alleged fraud and AOL's stock

fluctuations and let them speculate whether the former caused the

latter."     Bricklayers, 853 F. Supp. 2d at 190; cf. Milward, 639

F.3d at 17-19 (admitting expert testimony based on a subjective

"weight    of    the    evidence"    methodology,      but   identifying       the

established     steps    in   this   analysis    and   the   factors    used    in


                                      -30-
analyzing the causal relationship).    Dr. Hakala had tools at his

disposal, such as intra-day trading analysis, to guide his analysis

of confounding information.12

                 5.   Bottom Line

          Ultimately, we conclude that the district court did not

abuse its discretion in excluding Dr. Hakala's testimony. While we

may question its analysis with respect to dummy variables, the

court's treatment of the remaining three issues is more than

sufficient to satisfy our deferential review. See Ruiz-Troche, 161

F.3d at 83 ("[W]e will reverse a trial court's decision if we

determine that the judge committed a meaningful error in judgment."

(citations omitted) (internal quotation marks omitted)).

          Even conceding the aforementioned problems with Dr.

Hakala's event study, however, the shareholders contend that the

event study identified abnormal market movement, on certain key

dates, that did not suffer from any methodological infirmities.

Therefore, they claim, the district court abused its discretion by

throwing out the good with the bad.    True enough, some reviewing

courts have found abuses of discretion where trial courts rejected



     12
        Dr. Hakala could also have used content analysis.      See,
e.g., David Tabak, Making Assessments About Materiality Less
Subjective Through the Use of Content Analysis (2007), available at
http://www.nera.com/67_5197.htm; Esther Bruegger & Frederick C.
Dunbar, Estimating Financial Fraud Damages with Response
Coefficients, 35 J. Corp. L. 11, 25 (2009) ("'[C]ontent analysis'
is now part of the tool kit for determining which among a number of
simultaneous news events had effects on the stock price.").

                                -31-
mostly salvageable expert testimony for narrow flaws.          See City of

Tuscaloosa v. Harcros Chems., Inc., 158 F.3d 548, 563 (11th Cir.

1998) (reversing the exclusion of expert testimony in its entirety

where only "a small portion of [the] data and testimony [was]

fundamentally flawed").       Here, however, we confront the reverse

situation -- pervasive problems with Dr. Hakala's event study that,

allegedly, still leave a few dates unaffected.

            The district court was not obligated to prune away all of

the problematic events in order to preserve Dr. Hakala's testimony.

Out of fifty-seven event dates, the shareholders list five "key

disclosures" that should survive the district court's order.            The

district court did not abuse its discretion in treating the entire

event    study   as   inadmissible   given   the   overwhelming   imbalance

between unreliable and reliable dates.         The burden of proof falls

on the party introducing expert testimony.          Moore v. Ashland Chem.

Inc., 151 F.3d 269, 276 (5th Cir. 1998) ("The proponent need not

prove to the judge that the expert's testimony is correct, but she

must prove by a preponderance of the evidence that the testimony is

reliable.").      Requiring judges to sort through all inadmissible

testimony in order to save the remaining portions, however small,

would effectively shift the burden of proof and reward experts who

fill their testimony with as much borderline material as possible.

We decline to overturn the district court's ruling on this specious

logic.


                                     -32-
           We also reject the shareholders' argument that CSFB

ambushed them with new arguments at the Daubert hearing.13                          CSFB

presented no new arguments at the Daubert hearing.                      Instead, it

made a thorough presentation of the alleged problems of each event

date. This should not have caught the shareholders off guard. The

Daubert   hearing      occurred    over      three     years    after   CSFB    first

challenged Dr. Hakala's expert testimony.                      During those three

years,    CSFB    reiterated      its     arguments       in     expert     reports,

depositions, and briefings. It cited numerous examples of specific

dates, but never claimed that those dates constituted the entirety

of Dr. Hakala's flaws. The shareholders knew how CSFB would attack

Dr. Hakala's event study, and they could have anticipated the scope

of the attack.

           B.          Summary Judgment

           Our review of a grant of summary judgment is de novo,

interpreting     the    record    in   the     light    most    favorable      to   the

nonmoving party.        See Henry v. United Bank, 686 F.3d 50, 54 (1st

Cir. 2012).      "Under [Federal Rule of Civil Procedure 56(a)],

summary judgment is proper if the pleadings, depositions, answers

to interrogatories, and admissions on file, together with the

affidavits, if any, show that there is no genuine issue as to any

material fact and that the moving party is entitled to a judgment


     13
       The parties argue over which standard of review we should
apply to this issue. We need not answer that question, as the
outcome is the same under any standard of review.

                                        -33-
as a matter of law."       Celotex Corp. v. Catrett, 477 U.S. 317, 322

(1986) (internal quotation marks omitted).

          Although the district court awarded summary judgment to

CSFB   "even   if   [Dr.    Hakala's   event    study]   were   admitted,"

Bricklayers at 191-92, we need not engage in such counterfactual

analysis, see Peguero-Moronta v. Santiago, 464 F.3d 29, 34 (1st

Cir. 2006) ("We can affirm [the district court] on any basis

available in the record . . . .").             To sustain this suit, the

shareholders needed to show a connection between CSFB's deceptive

practices and the drop in AOL's stock price.             The shareholders

relied solely on Dr. Hakala's event study to satisfy this element.

Without it, they cannot show a genuine dispute as to this issue.

The district court did not need to tunnel into Dr. Hakala's event

study for any evidence favorable to the shareholders' claim.          The

district court excluded Dr. Hakala's testimony in its entirety. We

uphold that ruling.    Thus, there is no evidence to sort through,

and this complete lack of evidence compels a grant of summary

judgment to CSFB.

                              III. Conclusion

          For the foregoing reasons, we affirm the district court's

exclusion of the shareholders' expert testimony and consequently

affirm its award of summary judgment to CSFB.

It is so ordered.




                                   -34-
