Court Opinion

ID: 9964740
Source: CourtListenerOpinion
Date Created: 2024-04-30 18:00:47.960087+00
Date Added: 2024-06-11T08:25:40.562683
License: Public Domain

In the

     United States Court of Appeals
                  For the Seventh Circuit
                      ____________________
No. 23-1800
PIT ROW, INC., et al.,
                                                 Plaintiffs-Appellants,
                                  v.

COSTCO WHOLESALE CORPORATION,
                                                  Defendant-Appellee.
                      ____________________

          Appeal from the United States District Court for the
                    Eastern District of Wisconsin.
          No. 1:20-cv-00738 — William C. Griesbach, Judge.
                      ____________________

     ARGUED FEBRUARY 7, 2024 — DECIDED APRIL 30, 2024
                 ____________________

   Before WOOD, LEE, and PRYOR, Circuit Judges.
    WOOD, Circuit Judge. The plaintiﬀs in this appeal, a dozen
gas stations in the Green Bay, Wisconsin, area, contend that
Costco Wholesale Corporation (“Costco”) violated a Wiscon-
sin law that prohibits selling gasoline for less than the statu-
torily defined cost. They seek an injunction that prevents
Costco from selling gasoline below that level and over half a
million dollars each in damages. Costco argues that on nearly
every date at issue it lowered its prices only to match a
2                                                     No. 23-1800

competitor’s price, which the statute allows, and that in any
event, the plaintiﬀs failed to establish the causal element of
the statutory claim. The district court agreed with Costco and
awarded it summary judgment. The plaintiﬀs challenge that
decision, as well as an evidentiary ruling the court made ear-
lier in the proceedings. We aﬃrm on both counts.
                                 I
                           A. The Act
    At the center of this appeal lies Wisconsin’s Unfair Sales
Act, Wis. Stat. § 100.30 (“the Act”), commonly known as the
“Minimum Markup Law.” Like many similar laws that were
enacted by state legislatures after the first World War, the Act
purports to mandate trade-regulation concepts similar to
those that motivated the National Industrial Recovery Act of
1933, Pub. L. No. 73-67, 48 Stat. 195, invalidated by A.L.A.
Schechter Poultry Corp. v. United States, 295 U.S. 495 (1935). See,
e.g., IOWA CODE ANN. § 551.1–555.2, 551.4–551.11; MINN. STAT.
ANN. § 325D.03; see also Robinson-Patman Act of 1936, Pub.
L. No. 74-692, 49 Stat. 1526 (codified at 15 U.S.C. § 13). Wis-
consin’s Act has been modified several times over its eighty-
some-year life, but the policy underlying the legislation has
remained the same. The first provision of the Act states its ra-
tionale: “The practice of selling certain items of merchandise
below cost in order to attract patronage is generally a form of
deceptive advertising and an unfair method of competition in
commerce.” Wis. Stat. § 100.30(1).
   Motor-vehicle fuel (that is, gasoline) is one of the items of
merchandise covered by the Act. As relevant here, the law
makes loss leaders unlawful by prohibiting “[a]ny sale of any
item of merchandise … by a retailer … of motor vehicle
No. 23-1800                                                     3

fuel … , at less than cost as defined [by the Act] with the intent
or eﬀect of inducing the purchase of other merchandise or of
unfairly diverting trade from a competitor[.]” Id. § 100.30(3).
Formulas set forth in the statute determine the minimum law-
ful selling price in relation to the costs borne by the retailer.
See id. § 100.30(2)(am). The statutory definition of the cost of
motor-vehicle fuel is the greater of either invoice or replace-
ment cost plus a markup of 6%, or the average posted termi-
nal price plus a markup of 9.18%. See id.
§ 100.30(2)(am)(1m)(a). We refer to this as the “minimum
markup price.”
    The minimum markup requirement for motor-vehicle fuel
can be enforced by district attorneys, the Wisconsin Depart-
ment of Agriculture, Trade and Consumer Protection (“the
Department”), and private parties. The Act specifically af-
fords a private right of action for “[a]ny person who is injured
or threatened with injury as a result of a sale or purchase of
motor vehicle fuel” in violation of the Act. Id. § 100.30(5m). (A
separate Wisconsin statute provides that the word “person”
under state statutory law “includes all partnerships, associa-
tions and bodies politic or corporate.” Wis. Stat. § 990.01(26);
see also Village Food & Liquor Mart v. H & S Petroleum, Inc., 647
N.W.2d 177, 183 n.7 (Wis. 2002) (applying that statutory defi-
nition of “person” to the Act).) Private individuals may seek
either injunctive relief or the greater of treble damages or
$2,000, multiplied by each day of continued violation of the
Act. See Wis. Stat. § 100.30(5m). The Act also provides that
“[e]vidence of any sale of any item of merchandise by any re-
tailer … of motor vehicle fuel … at less than [the minimum
markup price] shall be prima facie evidence of intent or eﬀect
to … injure a competitor.” Id. § 100.30(3).
4                                                     No. 23-1800

    The Act lists nine exceptions to liability. See id. § 100.30(6);
§ 100.30(7)(c)(2). Relevant here is the seventh exception, see id.
§ 100.30(7), which the Wisconsin courts have referred to as the
“‘meeting competition’ exception,” see, e.g., Go America L.L.C.
v. Kwik Trip, Inc., 715 N.W.2d 746, 749 (Wis. Ct. App. 2006). Cf.
15 U.S.C. § 13(a) (Robinson-Patman’s “meeting competition”
defense). This exception states that the Act “shall not apply to
sales at retail … where … [t]he price of merchandise is made
in good faith to meet an existing price of a competitor and is
based on evidence in the possession of the retailer … in the
form of … [a] business record maintained by the retailer … in
the ordinary course of trade or the usual conduct of business.”
Id. § 100.30(6)(a)(7). An “existing price of a competitor” is “a
price being simultaneously oﬀered to a buyer for merchan-
dise of like quality and quantity by a person who is a direct
competitor of the retailer … and from whom the buyer can
practicably purchase the merchandise.” Id. § 100.30(2)(cj). A
retailer that lowers the price of motor-vehicle fuel in good
faith must “submit to the [D]epartment notification of the
lower price before the close of business on the day on which
the price was lowered[.]” Id. § 100.30(7)(a). “Failure to com-
ply” with the notification requirement “creates a rebuttable
presumption that the retailer … of motor vehicle fuel … did
not lower the price to meet the existing price of a competitor.”
Id. § 100.30(7)(b).
                          B. The Parties
    The plaintiﬀs are twelve corporations that each own and
operate a retail gas station in Green Bay, Wisconsin. (We refer
to them collectively as “the Green Bay Stations” unless con-
text requires otherwise.) They are open to all customers, un-
like defendant Costco. Anyone can buy gasoline from them,
No. 23-1800                                                     5

and no one must purchase other products or services from the
convenience stores attached to the stations as a condition of
obtaining their gasoline.
    Costco owns and operates members-only warehouses
across the country. Each warehouse oﬀers a “destination”
shopping experience with a wide array of products and ser-
vices, including (at many locations) motor-vehicle fuel.
Costco’s business model is predicated on bringing high-qual-
ity products to its members at the lowest possible prices. An-
yone can become a member and thus take advantage of what
Costco oﬀers, for a small fee; when a person becomes a mem-
ber, they must provide certain information, including an ad-
dress-of-record. In October 2013, Costco opened a warehouse
that oﬀers motor-vehicle fuel at 2355 Costco Way, Bellevue,
Wisconsin (“Bellevue Costco”), a village near the Green Bay
metropolitan area with about 14,500 residents.
    Costco uses a commercial gasoline-price reporting system
called PricePro to monitor the daily gasoline prices of 42 gas
stations that it considers to be direct competitors in the Green
Bay area. If a gas station is located within a five-mile radius of
the Bellevue Costco, then Costco automatically considers it a
direct competitor. In addition, it relies on employees and cus-
tomers of the Bellevue Costco to identify gas stations outside
that geographic area that might be direct competitors. When
a station is identified as a possible competitor, Costco’s Gas
Department turns to its “heat map” of the addresses-of-record
of Costco members who already have purchased gasoline at
the Bellevue Costco to determine whether a critical number of
them live near the potentially competing station or are likely
to pass by it on their way to the warehouse. If a suﬃcient
6                                                    No. 23-1800

number of gasoline-purchasing members live near the station,
Costco will deem it a direct competitor.
    The Bellevue Costco matches the gasoline prices oﬀered
by gas stations that it considers to be direct competitors. Its
employees physically verify the two or three lowest prices of-
fered each day; they also seek visual confirmation when a sus-
piciously low price is reported. (Costco largely suspended its
daily in-person verification procedures in early 2020 to com-
ply with stay-at-home requirements in place during the
COVID-19 pandemic, but otherwise has consistently abided
by the practice.) If Costco intends to match the price of gaso-
line oﬀered by a particular direct competitor, its Gas Depart-
ment records the reduced price in spreadsheets that collec-
tively are known as the “Comp Shop Log.”
     Three of the gas stations that the Bellevue Costco identi-
fied as direct competitors are relevant to this lawsuit. The first
is a BP gas station located at 601 Lawe Street in Kaukauna,
Wisconsin (“the Kaukauna BP”), which is about 24 miles (and
a 24-minute drive) from the Bellevue Costco. Costco’s records
indicate that upwards of 500 of its members with an address-
of-record in Kaukauna made at least one purchase inside the
Bellevue Costco warehouse between October 2019 and the
end of 2020, and that 236 members with such an address-of-
record collectively purchased gas 1,644 times at that ware-
house during that period. Although the Green Bay Stations
dispute whether all of the hundreds of members Costco iden-
tified actually live within the municipal boundaries of
Kaukauna, they concede that 236 members with an address-
of-record in Kaukauna purchased gasoline from the Bellevue
Costco between those dates.
No. 23-1800                                                  7

    Costco also matches the prices of two Marathon Stations
located in the Green Bay area (“the Marathon Stations”). Alt-
hough the Marathon Stations advertise only their “street” or
“sticker” price, they allow any customer to sign up for a re-
wards program known as MakeItCount Rewards. A customer
who joins MakeItCount Rewards needs only to swipe her mem-
bership card at the pump to save five cents per gallon of gas-
oline purchased. So, for example, if the sticker price oﬀered
by the Marathon Stations is $2.50 per gallon, a rewards mem-
ber will pay just $2.45 per gallon. The Bellevue Costco
matches the discounted price.
                       C. This Lawsuit
    The Green Bay Stations filed this lawsuit against Costco in
Wisconsin state court on March 30, 2020. Their third amended
complaint contends that Costco violated the Act on 256 days
between October 1, 2019, and December 31, 2020, by selling
regular unleaded motor-vehicle fuel at the Bellevue Costco
below the minimum markup price. (The Green Bay Stations
initially alleged violations on 263 days, but they later with-
drew their allegations against Costco for seven of those
days—March 3, 5, and 7–12, 2020.) They assert that Costco’s
gasoline-pricing practices threatened them with lower profit
margins and a reduction in customer volume, and that it ac-
tually injured them in those ways. The Green Bay Stations
seek $2,000 each per day of violation plus interest, attorneys’
fees, and a permanent injunction to prevent Costco from sell-
ing gasoline below the minimum markup price. They also
sought (unsuccessfully) to certify a class under Wisconsin law
consisting of all retailers of regular unleaded motor-vehicle
fuel who were competitors of the Bellevue Costco and who
8                                                  No. 23-1800

sold the fuel at or above Costco’s price during the 458-day pe-
riod set forth in the complaint.
   Costco timely removed the case to the Eastern District of
Wisconsin, invoking the court’s diversity jurisdiction. See 28
U.S.C. § 1441(b); 28 U.S.C. § 1332(d). It then moved for an or-
der compelling the Green Bay Stations to disclose all gasoline-
pricing data from October 1, 2017, to March 30, 2018, and all
gasoline sales-volume data for the period from October 1,
2017, to March 30, 2019. See FED. R. CIV. P. 37. Costco argued
that this data was necessary to prove whether the Green Bay
Stations suﬀered an actual injury or were threatened with in-
jury within the meaning of the Act. The Green Bay Stations
opposed the motion.
    In an order dated December 4, 2020, the district court
granted Costco’s motion to compel, explaining that the data
might be relevant to the question of constitutional standing.
Later, an exhibit entitled “Party Fuel Sale Trend Charts” was
produced; it contained data about daily gallons of gasoline
sold from October 1, 2017, through December 2020. Over that
time, each of the Green Bay Stations saw a downward trend
in gallons of gasoline sold per day. In separate submissions,
each plaintiﬀ testified through a corporate representative that
its profits had declined during the period 2017 through 2020.
All of the representatives also stated that they had received
questions from customers about why their prices for gasoline
were higher than Costco’s.
    Discovery continued into November 2021, when the
Green Bay Stations disclosed the expert report of a former
gasoline industry executive, Donald Strenk. He testified that
in his experience, a Costco entering a motor-vehicle-fuel mar-
ket poses a significant competitive threat to existing retailers
No. 23-1800                                                   9

in that market. Based on his professional experience and fa-
miliarity with price-elasticity modeling, Strenk said that he
was able to conclude to “a reasonable degree of certainty” that
the Green Bay Stations were at a minimum threatened by the
Bellevue Costco’s pricing practices.
    The Green Bay Stations also disclosed an expert report
from Paul Dingee, who served as the Chief of the Department
from July 1993 until January 2014. Dingee testified that when
a Costco warehouse enters a market for motor-vehicle fuel,
each existing retailer must make one of two pricing decisions:
it can either lower its prices to meet Costco’s, or it can main-
tain them and risk losing customers. And so, according to
Dingee, a retailer competing with a Costco would be pre-
sented with a Hobson’s choice: whichever route it chose, it
would suﬀer lost profits.
    Costco then disclosed expert reports from Alan Sorenson
and John Nevin, who are professors of economics and mar-
keting, respectively. Sorenson testified that he found no sta-
tistically significant correlation between the Bellevue Costco’s
pricing practices and the Green Bay Stations’ declining sales.
The Green Bay Stations responded with a “rebuttal” report
from Strenk, who claimed that a U.K.-based firm called Kali-
brate had generated a “sophisticated simulation model” that
showed Sorenson’s conclusion was “categorically false.”
When the Green Bay Stations refused to disclose the data un-
derlying the Kalibrate analysis, Costco moved to preclude it.
The district court granted the motion, ruling that the Green
Bay Stations could rely on neither the Kalibrate analysis nor
Strenk’s summary of it.
   Costco deposed Strenk on January 20, 2022. During the
deposition, Strenk informed Costco that after the Kalibrate
10                                                   No. 23-1800

analysis had been precluded he had conducted his own sta-
tistical analysis of the Green Bay Stations’ pricing and sales
data, and that he had shared the new analysis with the Green
Bay Stations a day ago. Three weeks later, the Green Bay Sta-
tions filed a motion to supplement their expert report with
Strenk’s new analysis. Costco opposed the motion, arguing
that the proposed supplement would undermine its discov-
ery eﬀorts in the midst of briefing on class certification and
summary judgment.
    The district court held a hearing on the motion on April
18, 2022. After hearing arguments from both sides, the court
observed that the time for disclosure had long passed, and
that Costco had conducted discovery in reliance upon the ex-
pert reports the Green Bay Stations already had disclosed. Al-
lowing the Green Bay Stations to supplement their expert re-
ports at the eleventh hour would force Costco either to redo
or to change the course of discovery and would thus prejudice
its defense. For these reasons, the court denied the Green Bay
Stations’ motion to supplement.
    On March 1, 2022, Costco moved for summary judgment
and for the denial of class certification. The district court
granted summary judgment to Costco and denied the Green
Bay Stations’ request to certify a class. (Its ruling on the class
aspects of the case is not before us on appeal, and so we do
not discuss it.) On the merits, the court concluded that for 238
days at issue, Costco was immune from liability pursuant to
the meeting-competition exception set forth in the Act. For the
No. 23-1800                                                             11

remaining 18 days,1 the district court found a genuine dispute
of fact about whether Costco sold gasoline below the mini-
mum markup, and thus determined that for those days
Costco could not assert immunity under the exception. None-
theless, it further concluded that for all 256 days, Costco was
entitled to summary judgment because the Green Bay Sta-
tions had failed to show that they were injured or threatened
with injury within the meaning of the Act. The Green Bay Sta-
tions now appeal the adverse award of summary judgment
and the earlier denial of their request to supplement their ex-
pert report.
                                    II
    Before we may address the merits of this appeal, we have
“an obligation to assure ourselves” that the litigants have Ar-
ticle III standing. DaimlerChrysler Corp. v. Cuno, 547 U.S. 332,
340 (2006) (quotation omitted). To maintain an action in fed-
eral court, a plaintiﬀ must have “(1) suﬀered an injury in fact,
(2) that is fairly traceable to the challenged conduct of the de-
fendant, and (3) that is likely to be redressed by a favorable
judicial decision.” Spokeo v. Robins, 578 U.S. 330, 338 (2016)
(citing Lujan v. Defs. of Wildlife, 504 U.S. 555, 560 (1992)). At the
summary judgment stage, the plaintiﬀ “must ‘set forth’ by af-
fidavit or other evidence ‘specific facts’” to support each ele-
ment, “which for purposes of the summary judgment motion
will be taken to be true.” Lujan, 504 U.S. at 561 (quoting FED.
R. CIV. P. 56(e)).

    1 Those 18 days are February 29, 2020; March 1–2, 4, and 6, 2020; April

14–15, 2020; June 26–30, 2020; September 2–3, 2020; and October 9, 11, 14,
and 17, 2020.
12                                                     No. 23-1800

    Little need be said about redressability. The Green Bay
Stations seek statutory damages and injunctive relief, both of
which are remedies that would “‘aﬀect the behavior of the de-
fendant towards the plaintiﬀ,’ and thus independently pro-
vide redress.” Uzuegbunam v. Preczewski, 141 S. Ct. 792, 801
(2021) (quoting Hewitt v. Helms, 482 U.S. 755, 761 (1987) (alter-
ation omitted)). We thus focus our attention on the first two
elements.
                         A. Injury in Fact
    The Green Bay Stations do not need to show that they have
a meritorious claim to satisfy the injury-in-fact requirement.
See Owsley v. Gorbett, 960 F.3d 969, 971 (7th Cir. 2020). But they
must “show that [they] suﬀered an invasion of a legally pro-
tected interest that is concrete and particularized and actual
or imminent, not conjectural or hypothetical.” Spokeo, 578 U.S.
at 339 (cleaned up). In plain English, a litigant is not required
to show that it will win in order to establish standing. All it
must do to satisfy Article III is show that it “ha[s] a colorable
claim to such a right.” Aurora Loan Servs. Inc. v. Craddieth, 442
F.3d 1018, 1024 (7th Cir. 2006). “Were we to require more than
a colorable claim, we would decide the merits of the case be-
fore satisfying ourselves of standing.” Booker-El v. Superinten-
dent, Indiana State Prison, 668 F.3d 896, 900 (7th Cir. 2012).
    We accept that the injury the Green Bay Stations alleged is
judicially cognizable. They claim that they suﬀered lost prof-
its and a decline in customer volume, and that they have a
legally protected interest in maintaining both their profits and
their customers. As the Supreme Court recently reminded us,
“monetary harms” are among the “most obvious” kinds of in-
jury in fact. TransUnion LLC v. Ramirez, 594 U.S. 413, 425
(2021); cf. Lexmark Intern., Inc. v. Static Control Components, Inc.,
No. 23-1800                                                     13

572 U.S. 118, 126 (2014) (indicating that “lost sales and dam-
ages to … business reputation” are injuries in fact).
    They also have proﬀered suﬃcient evidence of their al-
leged harms. Each of the Green Bay Stations introduced testi-
mony from a representative who claimed that their business
saw a decline in profits, as well as data showing a reduction
in their gasoline sales by volume, during the period stated in
the complaint. Given the nature of the claims that the Act au-
thorizes (i.e., actions for threatened or actual injury), that evi-
dence, taken as true, is enough to establish that the Green Bay
Stations have a colorable claim at the summary judgment
stage. See Warth v. Seldin, 422 U.S. 490, 500 (1975) (“Stand-
ing … often turns on the nature and source of the claim as-
serted.”); cf. Protect Our Parks, Inc. v. Chicago Park Dist., 971
F.3d 722, 736 (7th Cir. 2020) (noting that “when the existence
of a protected property interest is an element of the claim, de-
ciding whether the interest exists virtually always goes to the
merits rather than standing”).
                         B. Traceability
    A similar principle informs our traceability inquiry. This
element of standing “examines the causal connection between
the assertedly unlawful conduct and the alleged injury.” Allen
v. Wright, 468 U.S. 737, 753 n.19 (1984). Significantly, “[p]rox-
imate causation is not a requirement of Article III standing,
which requires only that the plaintiﬀ’s injury be fairly tracea-
ble to the defendant’s conduct.” Lexmark, 572 U.S. at 134 n.6.
An injury is not fairly traceable to a defendant’s conduct if the
causal chain is “attenuated,” Allen, 468 U.S. at 757, but Arti-
cle III requires no more than a “meaningful[] connect[ion]”
between the two, Dep’t of Ed. v. Brown, 600 U.S. 551, 568 (2023).
Put simply, a plaintiﬀ must show “a substantial likelihood”
14                                                   No. 23-1800

of causation. Duke Power Co. v. Envt’l Study Grp., Inc., 438 U.S.
59, 75 n.20 (1978).
    The record includes both lay and expert testimony stating
that Costco’s pricing practices at least threatened the Green
Bay Stations with the financial injuries they described. For ex-
ample, the Green Bay Stations retained an expert witness,
Dingee, who explained that, because of Costco’s business
model, when a Costco warehouse enters a market for motor-
vehicle fuel, the inevitable result for a retailer already in that
market will be diminishing returns: it will be forced either to
lower its prices (and thus lose profits) or to maintain its prices
(and thus lose customers and, in turn, profits). Strenk testi-
fied, specific to the parties to this case, that he was reasonably
certain that the Bellevue Costco’s pricing practices would, at
a minimum, pose a threat of lost profits to the Green Bay Sta-
tions. And representatives for each of the Green Bay Stations
testified that they believed Costco’s practices caused the fi-
nancial injuries the stations claim to have experienced.
    This evidence is enough to establish, for purposes of Arti-
cle III standing, a meaningful connection between Costco’s
pricing practices and the Green Bay Stations’ threat of injury.
Cf. Sanner v. Bd. of Trade of City of Chicago, 62 F.3d 918, 925–26
(7th Cir. 1995) (concluding that soybean farmers who were
forced to sell their product at a lower price had standing to
sue the Chicago Board of Trade where the allegations, taken
as true for purposes of a motion to dismiss, showed that a
conspiracy between the Board and several individuals
“played some role in setting the cash price for soybeans”). A
plaintiﬀ who asserts that he suﬀered from lost profits can es-
tablish the traceability element of causation at the summary
judgment stage by “present[ing] some evidence that he has
No. 23-1800                                                     15

lost money because [the defendant] forced him to set prices
artificially low” and that the customers “who purchased his
products would have paid more.” Slowiak v. Land O’Lakes, Inc.,
987 F.2d 1293, 1297 (7th Cir. 1993), overruled on other grounds
by Hill v. Tangherlini, 724 F.3d 965 (7th Cir. 2013). The Green
Bay Stations’ testimony does exactly that.
    We readily acknowledge that the line between “specific”
and “conclusory” allegations is a fine one. But the testimony
submitted by the Green Bay Stations was precise enough to
allow Costco to identify the particular conduct that allegedly
harmed the stations. In that connection, we emphasize that
the question at this point of the analysis is not whether the
testimony proves that Costco’s pricing practices caused harm
to the Green Bay Stations, but only whether it is suﬃcient to
show a substantial likelihood of causation. To require any-
thing more than what the Green Bay Stations have submitted
would conflate the standing inquiry with a determination on
the merits. The evidence presented here is enough to establish
the traceability element for purposes of Article III standing,
and so we may proceed.
                                III
    Before reaching the merits, we have a second preliminary
issue to resolve. The Green Bay Stations challenge the district
court’s order denying their motion to supplement Strenk’s ex-
pert report with his new analysis after the court refused to
admit the Kalibrate analysis. We review the district court’s
ruling for abuse of discretion. See Vance v. Ball State University,
646 F.3d 461, 469 (7th Cir. 2011).
   The Green Bay Stations moved to supplement Strenk’s ex-
pert report on February 11, 2022. By that time, discovery had
16                                                    No. 23-1800

been open for over two years, and nearly six months before
the motion Costco had disclosed its own expert report, which
included a cross-price elasticity analysis. Dispositive motions
on class certification and summary judgment were due in less
than three weeks, and yet, despite the looming deadlines, the
Green Bay Stations still allowed three weeks to pass after
Strenk informed Costco of his new analysis to file their motion
to supplement. On these facts, the district court was entitled
to conclude that allowing the supplement would be prejudi-
cial to Costco’s eﬀorts to prepare its defense. “We regularly
aﬃrm a district court’s decision to exclude supplemental evi-
dence in the interest of keeping cases moving forward,” id. at
469 (citing Pfeil v. Rogers, 757 F.2d 850, 858 (7th Cir. 1985)), and
we do so again here.
                                IV
    We arrive, finally, at the merits of the appeal. As we ex-
plained at the outset, the Green Bay Stations claim that Costco
threatened them with, and actually caused them, financial in-
jury by engaging in motor-vehicle-fuel pricing practices that
violated the Act on 256 days. The district court found that for
238 of those days, Costco was entitled to immunity from the
Green Bay Stations’ claim pursuant to the meeting-competi-
tion exception to the Act. See Wis. Stat. § 100.30(6)(a)(7). For
the remaining 18 days, the court concluded that the Green Bay
Stations had failed to establish that Costco’s conduct caused
them to suﬀer an injury or threat of injury within the meaning
of the Act. The Green Bay Stations challenge each of those
conclusions. We evaluate the district court’s grant of sum-
mary judgment de novo, construing the record in the light
most favorable to the Green Bay Stations and drawing all
No. 23-1800                                                     17

reasonable inferences in their favor. See Burton v. Downey, 805
F.3d 776, 783 (7th Cir. 2015).
           A. The Meeting-Competition Exception
    The Green Bay Stations argue that the district court erro-
neously concluded that the meeting-competition exception to
the Act immunizes Costco from liability on nearly all of the
alleged dates of violation. Costco qualifies for this exception
only if it was: (1) matching prices simultaneously oﬀered by a
direct competitor, (2) compliant with the Act’s notification re-
quirement, and (3) price-matching in good faith. See 22
Shawano, LLC v. Dr. R.C. Samanta Roy Inst. of Sci. and Tech., Inc.,
709 N.W.2d 98, 101–02 (Wis. Ct. App. 2005) (noting that a re-
tailer who complies with the exception “is immune from lia-
bility in a private action”). We address these elements sequen-
tially.
            1. Existing Price of a Direct Competitor
    The meeting-competition exception does not apply unless
a retailer lowered its prices (or maintained already lowered
prices) to match the “existing price of a competitor,” Wis. Stat.
§ 100.30(6)(a)(7), which the Act in turn defines as “a price be-
ing simultaneously oﬀered to a buyer for merchandise of like
quality and quantity by a person who is a direct competitor of
the retailer … of motor vehicle fuel … and from whom the
buyer can practicably purchase the merchandise,” id.
§ 100.30(2)(cj). Costco argues that it met the prices oﬀered by
the Kaukauna BP and matched the five-cent discounted price
oﬀered to customers of the Marathon Stations through
MakeItCount Rewards. It submitted evidence showing that it
lowered its prices to match those of the Kaukauna BP on 22
days and those of the Marathon Stations on 89 days, and that
18                                                  No. 23-1800

for all but 18 of the days that its gasoline was priced below the
minimum markup price from October 1, 2019, to December
31, 2020, it was so priced in order to match one or the other of
these competitors.
   For their part, the Green Bay Stations do not contest that
Costco matched the prices of the Kaukauna BP and the Mara-
thon Stations. They instead argue that Costco was not entitled
to match their prices for purposes of the exception.
                        i. Kaukauna BP
    The Kaukauna BP is not a direct competitor of the Bellevue
Costco, the Green Bay Stations contend, because it is in a dif-
ferent and more distant geographic area than every other gas
station that Costco identifies as a direct competitor on its
“heat map.” They stress that the Kaukauna BP is not in the
city of Green Bay, that the land between Green Bay and
Kaukauna is only lightly developed, and that the Kaukauna
BP is roughly 24 miles from the Bellevue Costco. Moreover,
they say, although a separate Costco warehouse in Appleton,
Wisconsin, is closer to the Kaukauna BP than the Bellevue
Costco by nearly seven miles, the Appleton Costco does not
consider the Kaukauna BP to be its direct competitor. Costco
responds that the Kaukauna BP is a direct competitor because
the Bellevue Costco is competing for buyers who could (and
do) purchase gasoline from either retailer.
   A decision from a Wisconsin intermediate court sheds
some light on the meaning of “direct competitor” for this pur-
pose. See Go America, 715 N.W.2d at 751. Without distinguish-
ing between “direct competitor” and “competitor,” the court
concluded that the phrase refers to “one selling or buying
goods or services in the same market as another.” Id. at 806
No. 23-1800                                                   19

(quotation omitted). Go America thus indicates that, to resolve
whether the Kaukauna BP is the Bellevue Costco’s direct com-
petitor, we must define the relevant market. If Costco is sell-
ing gasoline in the same market as the Kaukauna BP, then the
two retailers are direct competitors.
    We know from long experience with antitrust cases that an
elaborate definition of the relevant market is neither neces-
sary nor, in some cases, possible. See Federal Trade Commission
v. Indiana Federation of Dentists, 476 U.S. 447, 460–61 (1986)
(concluding that “the finding of actual, sustained adverse ef-
fects on competition [in the areas where the dentists] predom-
inated, viewed in light of the reality that markets for dental
services tend to be relatively localized, is legally suﬃcient to
support a finding that the challenged restraint was unreason-
able even in the absence of elaborate market analysis”). It of-
ten is enough to approximate the outer boundaries of a prod-
uct or geographic market.
    For guidance on how to approximate the relevant market,
we consult the federal Merger Guidelines. The Guidelines
state: “A relevant antitrust market is an area of eﬀective com-
petition, comprising both product (or service) and geographic
elements. The outer boundaries of a relevant product market
are determined by the ‘reasonable interchangeability of use or
the cross-elasticity of demand between the product itself and
substitutes for it.’” U.S. DEP’T OF JUSTICE & FED. TRADE
COMM’N, MERGER GUIDELINES 40 (2023) (quoting Brown Shoe
Co. v. United States, 370 U.S. 294, 325 (1962)). Because “‘fuzzi-
ness would seem inherent in any attempt to delineate the rel-
evant market,’” the Guidelines recommend identifying cer-
tain kinds of evidence that may help “to identify a relevant
antitrust market.” Id. (quoting United States v. Philadelphia
20                                                  No. 23-1800

Nat’l Bank, 374 U.S. 321, 360 n.37 (1963) (ellipsis omitted)).
Helpful evidence includes “[d]irect evidence of substantial
competition between” retailers and “practical indicia,” “such
as … the product’s peculiar characteristics and uses, … dis-
tinct customers, … and specialized vendors.” Id. at 40–41.
    The Merger Guidelines show that the Green Bay Stations
place far too much weight on geography in their attempt to
define the relevant market. The fact that the Kaukauna BP is
24 miles from the Bellevue Costco, and significantly further
from the warehouse than any of the other retailers that Costco
considers direct competitors, is not dispositive of whether the
two are direct competitors. Gasoline is a product for which
consumers can (and will) travel some distance. More broadly,
the point is that we must attend not only to geography, but
also to the specific characteristics of the product being oﬀered
and the customers to whom it is being oﬀered, among other
practical considerations.
    Following that approach, it is evident that Costco shares a
market with the Kaukauna BP. As we have noted several
times, the parties agree that 236 Costco members with an ad-
dress-of-record in Kaukauna have purchased gasoline at the
Bellevue Costco during the applicable 458-day period. These
customers are distinct, insofar as they are members of Costco.
But to point out that fact is merely to highlight that Costco has
a unique membership structure: unlike the typical customer
of the Kaukauna BP, a person who is a member of Costco can
take advantage of any of its services, including its gasoline
pumps. And, as the testimonies of numerous Costco members
show, it is not uncommon to purchase gasoline at Costco
while visiting the warehouse to purchase other products.
Costco thus has an interest in encouraging its members who
No. 23-1800                                                  21

reside in Kaukauna to purchase gasoline at the Bellevue ware-
house—i.e., to compete with the Kaukauna BP for customers.
     We add that it is far from impracticable for a Costco mem-
ber with an address-of-record in Kaukauna to purchase gaso-
line at the Bellevue Costco, rather than at the Kaukauna BP. A
person easily could drive 24 miles on very little gasoline; they
might already have planned to visit the warehouse for some
other product or service and simply added gasoline to the list.
Alternatively, they might be in the area for some other reason
and choose to take advantage of their Costco membership by
filling up their tank.
   In sum, we conclude that, owing to its membership struc-
ture, Costco’s direct competitors should be determined not
simply based on the location of the stations, but also on the
addresses-of-record of its members. Although there might be
some number of customers that is too few to establish the nec-
essary competition, we need not decide here where the lower
threshold lies. We are confident that the existence of 200-plus
buyers who could practicably purchase gasoline from either
the Kaukauna BP or Costco places those two retailers in the
same motor-vehicle-fuel market and thus makes them direct
competitors for purposes of the Act.
                     ii. Marathon Stations
    Costco did not lower its prices to match only the
Kaukauna BP’s prices; on some days, it lowered or matched
the prices oﬀered by the Marathon Stations. The Green Bay
Stations argue that the Marathon Stations are not direct com-
petitors of Costco, but for a diﬀerent reason than they be-
lieved the Kaukauna BP is not. They do not dispute that the
Marathon Stations are in the same market as Costco or that
22                                                   No. 23-1800

buyers could practicably purchase gasoline from any of those
three retailers. Rather, seizing onto the statutory language
stating that an “[e]xisting price of a competitor” is a “price
being simultaneously oﬀered to a buyer,” Wis. Stat.
§ 100.30(2)(cj) (emphasis added), they argue that the Mara-
thon Stations advertised only the sticker price to buyers, not
the five-cent reduced price available through MakeItCount Re-
wards, and thus did not “oﬀer” the discounted price to its cus-
tomers.
    As the district court noted, the text of the Act does not re-
strict a retailer to matching the posted price of its competitors.
The terms are broad enough to allow for the matching of any
price oﬀered to a buyer, whether that price is advertised or
not. Costco was therefore entitled to match the prices oﬀered
through MakeItCount Rewards, notwithstanding the fact that
the Marathon Stations did not advertise them.
    The Green Bay Stations insist that this interpretation of the
Act is incorrect. As support, they point to two sources: a deci-
sion from a Wisconsin state trial court and a regulation prom-
ulgated by the Department that interprets the meeting-com-
petition exception. The former does not help their position, as
our role as a federal court sitting in diversity is to ascertain
how the state appellate courts would interpret the Act. See
West v. American Tel. & Tel. Co., 311 U.S. 223, 237–38 (1940).
The Wisconsin appellate courts consistently have stated that
courts “should not read into the statute language that the leg-
islature did not put in.” Brauneis v. State, Labor and Industry
Review Comm’n, 612 N.W.2d 635, 644 (Wis. 2000) (citing In re
G. & L.P., 349 N.W.2d 743 (Wis. 1984)). We cannot, consistent
with this principle of construction, interpret “oﬀered to the
buyer” as “advertised to the buyer” or “oﬀered to the buyer
No. 23-1800                                                  23

in the form of an advertisement,” as the Green Bay Stations
would have us do.
    The Department’s regulation provides that “[a] price for
merchandise meets an existing price of a competitor under
[the Act] only if the merchandise in question is sold on a day
when the competitor’s price is in eﬀect and is oﬀered under
the same terms and conditions as the competitor’s oﬀer.” Wis.
Admin. Code § ATCP 105.009. The Green Bay Stations argue
that Costco oﬀered diﬀerent “terms and conditions” to buyers
than the Marathon Stations.
    The state agency’s interpretation of the Act is less helpful
than the Green Bay Stations think. Wisconsin courts no longer
defer to administrative agencies’ conclusions of law, but they
do “give ‘due weight’ to the experience, technical compe-
tence, and specialized knowledge of an administrative
agency.” Tetra Tech EC, Inc. v. Wisconsin Dep’t of Revenue, 914
N.W.2d 21, 63 (Wis. 2018). That said, we need not decide how
much weight to give to the Department’s regulation. Even as-
suming that its interpretation of the Act is correct, the Green
Bay Stations would not prevail because Costco did oﬀer the
same terms and conditions as the Marathon Stations. Anyone
can become a member of either Costco or the MakeItCount Re-
wards program (or both), and neither Costco nor the program
placed gallon restrictions on their prices. The sole diﬀerence
between the programs—that Costco members must pay a
small membership fee—is immaterial because Costco does
not compete for motor-vehicle-fuel buyers who are not al-
ready members. Thus, to the extent that the regulation sheds
light on the meaning of the Act, it does not undermine our
conclusion.
24                                                  No. 23-1800

    The Act places no limitation on what prices a retailer may
match; it says only that they must be oﬀered to a buyer. The
Marathon Stations are in the same market as Costco and they
oﬀered the MakeItCount Rewards prices to all customers.
Costco was therefore permitted to match the prices of those
retailers. Accordingly, for 238 of the days at issue, Costco was
matching the prices oﬀered by its direct competitors.
               2. The Notification Requirement
    A retailer cannot claim immunity simply by showing that
it lowered its prices to match those oﬀered by a direct com-
petitor; it must also satisfy the Act’s notification requirement.
The Act states that “[i]f a retailer … of motor vehicle
fuel … lowers in good faith the price of motor vehicle fuel be-
low [the minimum markup price] under [the meeting-compe-
tition exception], the person shall submit to the [D]epartment
notification of the lower price before the close of business on
the day on which the price was lowered[.]” Wis. Stat.
§ 100.30(7)(a). A retailer’s failure to comply with this require-
ment does not prevent it from asserting a defense under the
Act. It merely “creates a rebuttable presumption” that the re-
tailer did not lower its prices to meet the existing price of a
competitor. Id. § 100.30(a)(b).
    The district court concluded that, although Costco inad-
vertently submitted notifications to the Department listing the
incorrect competitor on fifty days in which it lowered its
prices to match a competitor, Costco overcame the presump-
tion that it did not lower its price for a permissible purpose
by introducing business records confirming its compliance
with the requirements of the exception. On appeal, the Green
Bay Stations do not challenge the court’s conclusion. Wisely
so: the Act allows a retailer to introduce business records
No. 23-1800                                                  25

maintained in the usual course of business to prove that it
matched the prices of a direct competitor. See id.
§ 100.30(6)(a)(7). Costco introduced spreadsheets that it calls
its “Comp Shop Log,” which it updated daily during the rel-
evant period whenever it matched the price oﬀered by a com-
petitor. That document was maintained in its usual course of
business, and so it falls within the “other business record”
catchall listed in the notification-requirement provision of the
Act. This suﬃces to rebut the presumption that Costco’s occa-
sional, unintentional non-compliance with the notification re-
quirement removes it from the safe harbor of the meeting-
competition exception.
                        3. Good Faith
    The final element of the statutory exception requires an in-
quiry into Costco’s motive or intent. The Act states that a re-
tailer’s decision to lower prices to match those of a competitor
must be “made in good faith[.]” Wis. Stat. § 100.30(6)(a)(7).
Although the Wisconsin courts have been “reluctant to re-
solve” where the burden of proving good (or bad) faith falls,
see Go America, 715 N.W.2d at 754–55, the case law oﬀers some
clues. In Go America, the Wisconsin Court of Appeals assumed
for purposes of argument that the defendant aﬃrmatively
had to demonstrate its good faith. The defendant introduced
testimony that it surveyed its competitors’ gasoline prices
daily in order to match them, and it submitted copies of its
price surveys to support that testimony. The plaintiﬀ, by con-
trast, failed to introduce anything to “show or create a reason-
able inference to the contrary.” Id. at 756. On that record, the
court concluded that the defendant had price-matched in
good faith.
26                                                 No. 23-1800

    The evidence tending to show Costco’s motive is substan-
tially identical to the evidence presented by the defendant in
Go America. Costco has introduced evidence that it monitored
its competitors on a daily basis, made eﬀorts to comply with
the notification requirement, and kept business records to
show its diligence even when it did not notify the Department
of its price-matching. The Green Bay Stations, on the other
hand, can point only to complaints against Costco submitted
to the Department. But unsubstantiated complaints do not
reasonably give rise to an inference of bad faith, and so even
assuming Costco must establish its good faith, it has done so.
     B. The Elements of the Act’s Private Right of Action
    The Green Bay Stations next argue that the district court
erroneously concluded that they failed to establish that
Costco’s pricing practices caused them to suﬀer an injury or
threat of injury. Because Costco has shown that it is entitled
to immunity under the meeting-competition exception for 238
of the days at issue, we need decide only whether Costco in-
jured or threatened the Green Bay Stations with injury on the
remaining 18 days. See supra n.1. The burden is on the Green
Bay Stations to establish each element of their claim. See Hei-
den v. Ray’s Inc., 150 N.W.2d 467, 470–71 (Wis. 1967).
    Like the district court, we begin with the statutory element
of causation. To determine whether the Green Bay Stations
have carried their burden of proving causation, we must first
determine what it means for a person to be “injured or threat-
ened with injury as a result of a sale or purchase of motor ve-
hicle fuel” below the minimum markup price. Wis. Stat.
§ 100.30(5m) (emphasis added). Although the Wisconsin
courts have not considered what theory of causation is incor-
porated into the Act by that phrase, they long have held that
No. 23-1800                                                   27

a person’s conduct causes a particular result when it is a sub-
stantial factor in producing that result. See, e.g., Lang v. Bau-
mann, 251 N.W. 461 (Wis. 1933); Fischer by Fischer v. Ganju, 485
N.W.2d 10 (Wis. 1992). The Act, which was adopted shortly
after Baumann, thus requires the Green Bay Stations to show
that Costco’s pricing practices were a substantial factor in
causing their lost profits.
    In their eﬀort to make that showing, all but one of the
Green Bay Stations exclusively rely on the expert reports pre-
pared by Strenk and Dingee. As we explained earlier, Strenk
testified, without data, that he could conclude “to a reasona-
ble degree of certainty” that the Bellevue Costco at least
threatened the Green Bay Stations’ sales volume. Both of the
experts testified that a Costco entering a market would
threaten existing retailers with injury. One plaintiﬀ, Tikapur
Petroleum, LLC, also submitted a declaration of a corporate
representative who stated that his “general observation” was
that his profits and sales were declining and that he “believed
this was attributable to Costco’s low gas pricing.”
    The evidence the Green Bay Stations oﬀer is not suﬃcient
to prove causation for purposes of the Act. In the absence of
any rigorous market or economic analysis (or even evidence
that at least one customer actually elected to purchase gaso-
line from Costco rather than from the Green Bay Stations be-
cause Costco oﬀered lower prices), the testimony upon which
the Green Bay Stations rely amounts to little more than “sheer
speculation,” which the Wisconsin Supreme Court has held is
insuﬃcient to establish an element of the Act’s private cause
of action. Heiden, 150 N.W.2d at 638–39. Indeed, in Heiden, the
court went so far as to say that a proven fact of a single inci-
dent of a lost sale is not “suﬃcient to establish a prima facie
28                                                   No. 23-1800

loss or threat of injury.” Id. at 638. The Green Bay Stations
have not introduced evidence that Costco’s pricing practices
caused even one lost sale. They thus have failed to establish
causation, which is an essential element of their claim. This
means that Costco is entitled to summary judgment on the re-
maining 18 days stated in the complaint.
                                V
    The Act exists to prevent “unfair method[s] of competition
in commerce,” not to interfere with retailers “who maintain a
fair price policy.” Wis. Stat. § 100.30(1). When a retailer of mo-
tor-vehicle fuel complies with the requirements the statute
imposes on its ability to match the prices of a direct competi-
tor, it is engaged in lawful competition. And even when it
does not, a plaintiﬀ cannot obtain judicial relief unless it can
establish the essential elements of the private right of action.
The Green Bay Stations have failed to raise a triable issue of
fact with respect to causation, and thus they cannot prevail.
     The judgment of the district court is AFFIRMED.