M & K Employee Solutions, Inc. v. Trustees of IAM Nat. Pension

P R E L I M I N A R Y P R I N T
Volume 608 U. S. Part 1
Pages 264–277
OFFICIAL REPORTS
OF
THE SUPREME COURT
May 21, 2026
REBECCA A. WOMELDORF
reporter of decisions
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264 OCTOBER TERM, 2025
Syllabus
M & K EMPLOYEE SOLUTIONS, LLC, et al. v.
TRUSTEES OF THE IAM NATIONAL PENSION
FUND
certiorari to the united states court of appeals for
the district of columbia circuit
No. 23–1209. Argued January 20, 2026—Decided May 21, 2026
Pursuant to the Employee Retirement Income Security Act of 1974
(ERISA), as amended, an employer that stops participating in an under-
funded Multiemployer Pension Plan (MPP), must pay the plan “with-
drawal liability,” i.e., the employer's share of the plan's unfunded vested
benefts (UVBs). See 29 U. S. C. § 1391. Withdrawal liability is calcu-
lated based on the plan's UVBs “as of ” the statutory measurement
date—the last day of the plan year preceding the employer's with-
drawal. §§ 1391(b)(2)(E)(i), (c)(2)(C)(i), (3)(A), (4)(A). Determining the
value of a plan's UVBs depends upon both hard data (such as the num-
ber of benefciaries and the value of the plan's assets) and a variety of
actuarial predictions about the future. One key actuarial assumption
is the discount rate, which is the interest rate “used to discount future
beneft payments to their present value.” 87 Fed. Reg. 62317.
Petitioners are four employers who withdrew from the IAM National
Pension Fund (Fund)—an underfunded MPP—between April and De-
cember 2018. The Fund assessed each employer's withdrawal liability
“as of ” December 31, 2017 (the measurement date). In making this
calculation, the Fund applied a discount rate of 6.50%, which it had
adopted with its actuarial frm in January 2018. The Fund had pre-
viously used a discount rate of 7.50% to value its UVBs. Petitioners
each initiated arbitrations challenging their assessments. In each case,
the arbitrators determined that the assessments were erroneous be-
cause the Fund had applied actuarial assumptions adopted after the
measurement date. The arbitrators instead required the Fund to use
the actuarial assumptions that were “in effect” on the measurement
date—i.e., the 7.50% discount rate. App. 293. The Fund sought re-
view in Federal District Court. The courts disagreed with the arbitra-
tors and held that actuaries could use assumptions adopted after the
measurement date. The D. C. Circuit affrmed in a consolidated appeal.
Its decision conficted with a decision of the Second Circuit, and this
Court granted certiorari to resolve when actuarial assumptions may be
selected for purposes of calculating withdrawal liability.

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Cite as: 608 U. S. 264 (2026) 265
Syllabus
Held: The provisions of ERISA governing the calculation of withdrawal
liability—§§ 1391 and 1393—do not require the actuarial assumptions
underlying that calculation to be selected on or before the measurement
date. Pp. 271–277.
(a) Section 1391 requires withdrawal liability to be calculated based on
the value of a plan's UVBs “as of ” the measurement date. Petitioners
contend that § 1391's “as of ” language establishes a deadline for the se-
lection of actuarial assumptions. But § 1391 sets no such deadline.
The term “as of ” is understood “to assign an event to one time and the
recognition of it to another.” W. Follett, Modern American Usage 41.
Section 1391's “as of ” language thus means that the hard data that feeds
the UVB calculation must be fxed on the measurement date, but the
calculation itself can be performed after that date. Actuarial assump-
tions are not observable facts about the plan; instead, they are predic-
tive judgments used as tools to calculate UVBs. Accordingly, while
§ 1391's “as of ” requirement sets the reference point for factual inputs,
it has no bearing on when actuaries must select their assumptions.
Pp. 271–274.
(b) Section 1393, which governs the use of actuarial assumptions for
assessing withdrawal liability, states that the assumptions must be “rea-
sonable,” “tak[e] into account the experience of the plan and reasonable
expectations,” and “offer the actuary's best estimate of anticipated expe-
rience under the plan.” § 1393(a)(1). Section 1393 provides no dead-
line by which actuaries must select their assumptions, and the Court
does not generally read limitations into statutes that do not appear in
their text. Romag Fasteners, Inc. v. Fossil Group, Inc., 590 U. S. 212,
215. Indeed, because Congress included a deadline for the selection of
actuarial assumptions in a different section of the statute, but imposed
no similar limit in § 1393, the Court presumes that the omission in § 1393
is intentional. See Russello v. United States, 464 U. S. 16, 23. More-
over, § 1393's instruction that actuarial assumptions refect the actuary's
“best estimate,” § 1393(a)(1), supports the conclusion that actuaries can
select their assumptions after the measurement date. Requiring actu-
aries to use assumptions selected before the measurement date could
prevent them from relying on the most up-to-date data when selecting
their assumptions, resulting in assumptions that do not refect their
“best estimate.” Pp. 274–275.
(c) Petitioners' remaining arguments do not overcome the absence of a
textual deadline for adopting actuarial assumptions. First, petitioners
point to a different provision of ERISA that prohibits plans from apply-
ing any new “plan rule or amendment” to an employer's withdrawal
liability if the rule or amendment is adopted after the employer with-

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266 M & K EMPLOYEE SOLUTIONS, LLC v. TRUSTEES OF
IAM NAT. PENSION FUND
Syllabus
draws. § 1394(a). But the retroactivity limits in § 1394 concededly do
not apply to actuarial assumptions. Congress chose not to enact a simi-
lar antiretroactivity rule in § 1393, and inferring one would override
Congress's choice.
Petitioners fall back on a policy argument, contending that allowing
plans to adopt actuarial assumptions after the measurement date will
invite manipulation, enabling plans and their actuaries to retroactively
select assumptions in order to increase withdrawing employers' liability.
But petitioners' proposed rule does not address these concerns, and in
any event, “policy concerns cannot trump the best interpretation of the
statutory text.” Patel v. Garland, 596 U. S. 328, 346. Congress chose
which limits to impose on the selection of actuarial assumptions, and it
is not the role of the Court to supplant Congress's choices. Pp. 275–277.
92 F. 4th 316, affrmed.
Jackson, J., delivered the opinion for a unanimous Court.
Michael E. Kenneally, Jr., argued the cause for petition-
ers. With him on the briefs were Andrew R. Hellman, Deb-
orah S. Davidson, Donald J. Vogel, R. Jay Taylor, Jr., James
A. Eckhart, Jonathan Janow, and William P. Lewis.
John E. Roberts argued the cause for respondent. With
him on the brief were Myron D. Rumeld, Mark D. Harris,
Neil V. Shah, Lena H. Hughes, and Lucas Kowalczyk.
Kevin J. Barber argued the cause for the United States as
amicus curiae urging affrmance. With him on the brief
were Solicitor General Sauer, Deputy Solicitor General
Gannon, and Karen L. Morris.*
*Briefs of amici curiae urging reversal were fled for the Chamber of
Commerce of the United States of America by Jonathan S. Franklin and
Gregory Ossi; and for the HR Policy Association by Sarah Bryan Fask.
Briefs of amici curiae urging affrmance were fled for AARP et al. by
Rachel N. Lokken, Louis Lopez, and William Alvarado Rivera; for the
American Federation of Labor and Congress of Industrial Organizations
by Matthew J. Ginsburg and Darin M. Dalmat; for the National Coordi-
nating Committee for Multiemployer Plans by Paul A. Green; for the Pen-
sion Rights Center by Israel Goldowitz and Theresa S. Gee; and for the
Segal Group, Inc., et al. by Samuel I. Levin.
Mark M. Trapp fled a brief for James P. Naughton as amicus curiae.
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Cite as: 608 U. S. 264 (2026) 267
Opinion of the Court
Justice Jackson delivered the opinion of the Court.
An employer that stops participating in an underfunded
Multiemployer Pension Plan must pay the plan “withdrawal
liability”—i. e., its share of the plan's unfunded vested bene-
fts. Calculating the unfunded vested benefts is a compli-
cated endeavor because the plan's actuary must predict the
value of the plan's future assets and obligations. To do so,
the actuary makes certain assumptions about, for example,
retirees' life expectancies and the anticipated growth rate of
the plan's investments. By statute, an employer's with-
drawal liability is based on the value of the plan's unfunded
vested benefts “as of ” the last day of the plan year preceding
the employer's withdrawal, also known as the measurement
date. 29 U. S. C. § 1391.
The question presented in this case is whether the “as of ”
language sets the measurement date as the deadline by
which actuaries must select the assumptions that underlie
the withdrawal-liability calculation. The Court of Appeals
for the D. C. Circuit held that it does not, concluding that
actuaries may select their assumptions after the measure-
ment date. We agree. The statute governing the selection
and use of actuarial assumptions in the withdrawal-liability
context contains no requirement that actuaries use assump-
tions adopted prior to the measurement date.
I
A
The Employee Retirement Income Security Act of 1974
(ERISA) provides “comprehensive regulation for private
pension plans.” Connolly v. Pension Beneft Guaranty
Corporation, 475 U. S. 211, 214 (1986). One type of pension
plan that ERISA regulates is a Multiemployer Pension Plan
(MPP). An MPP is a plan “to which more than one em-
ployer contributes” and is “maintained to fulfll the terms of
collective-bargaining agreements.” Concrete Pipe & Prod-
ucts of Cal., Inc. v. Construction Laborers Pension Trust
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268 M & K EMPLOYEE SOLUTIONS, LLC v. TRUSTEES OF
IAM NAT. PENSION FUND
Opinion of the Court
for Southern Cal., 508 U. S. 602, 605 (1993); see 29 U. S. C.
§ 1002(37).
As amended by the Multiemployer Pension Plan Amend-
ments Act of 1980, ERISA requires employers that with-
draw from an underfunded MPP to pay “withdrawal liabil-
ity.” § 1381(a); see Milwaukee Brewery Workers' Pension
Plan v. Jos. Schlitz Brewing Co., 513 U. S. 414, 417 (1995).
Withdrawal liability refects the employer's share of the
plan's unfunded vested benefts (UVBs)—that is, the dif-
ference between the present value of the benefts owed to
employees and the current value of the plan's assets.
§§ 1381(b)(1), 1393(c). By requiring employers to pay their
share of the UVBs, ERISA seeks to ensure that plans do not
become insolvent when employers withdraw. Milwaukee
Brewery, 513 U. S., at 416–417.
Section 1391 specifes the methods that plans may use to
calculate withdrawal liability. The common feature of each
method is the requirement that withdrawal liability be calcu-
lated based on the plan's UVBs “as of ” the last day of the
plan year preceding the employer's withdrawal—the meas-
urement date. See §§ 1391(b)(2)(E)(i), (c)(2)(C)(i), (3)(A),
(4)(A); Milwaukee Brewery, 513 U. S., at 417–418.
Determining a plan's UVBs is not a matter of simple arith-
metic. The value of the UVBs depends upon both hard data
about the plan (such as the number of benefciaries and the
value of the plan's assets) and a variety of predictions about
the future. For example, how many employees will draw on
their benefts and for how long? And what is the value of
those future benefts in today's dollars?
To make these predictions, a plan's actuary must select
demographic and economic assumptions about how the plan's
assets and obligations will change over time. American
Academy of Actuaries, Issue Brief: Selection of Actuarial As-
sumptions for Multiemployer Plans 3 (July 2020). A key ac-
tuarial assumption—the one relevant here—is the discount
rate: the interest rate “used to discount future beneft pay-

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Cite as: 608 U. S. 264 (2026) 269
Opinion of the Court
ments to their present value.” 87 Fed. Reg. 62317 (2022);
see Actuarial Standards Board, Actuarial Standard of Prac-
tice No. 27, § 3.3 (2023) (ASOP). A higher discount rate re-
duces the value of the plan's UVBs. 87 Fed. Reg. 62317.
Lower UVBs, in turn, correspond to a lower withdrawal lia-
bility for employers. Ibid.
Actuaries select the assumptions underlying their UVB
calculations based on relevant “current and historical data,”
ASOP No. 27, § 3.5, including growth in the plan's earnings,
infation, yields on securities, and other macroeconomic con-
ditions, id., § 3.7. ERISA imposes few substantive require-
ments on the selection of these assumptions. Section 1393,
which governs the use of actuarial assumptions in calculating
withdrawal liability, says only that the actuary must use “ac-
tuarial assumptions and methods which, in the aggregate,
are reasonable (taking into account the experience of the
plan and reasonable expectations) and which, in combination,
offer the actuary's best estimate of anticipated experience
under the plan.” § 1393(a)(1).1
B
The IAM National Pension Fund (Fund) is an MPP serv-
ing employees who are covered by collective bargaining
agreements with the International Association of Machinists
and Aerospace Workers. In November 2017, its actuarial
frm, Cheiron, published the annual valuation of the Fund's
assets and liabilities for the 2016 Plan Year. Using a dis-
count rate of 7.50%, Cheiron valued the Fund's UVBs at
close to $500 million. Two months later, on January 24,
2018, Cheiron met with the Fund's trustees to discuss the
actuarial assumptions it would use to calculate withdrawal
liability for employers who withdrew in 2018. They settled
on a discount rate of 6.50%, 1% lower than the rate pre-
1 In the alternative, the actuary can use “assumptions and methods set
forth in the [Pension Beneft Guaranty Corporation's] regulations.” 29
U. S. C. § 1393(a)(2); see § 1301(a)(4). This alternative is not at issue here.
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270 M & K EMPLOYEE SOLUTIONS, LLC v. TRUSTEES OF
IAM NAT. PENSION FUND
Opinion of the Court
viously used. Cheiron published its actuarial valuation for
Plan Year 2017 on April 17, 2019. Using the 6.50% discount
rate, it valued the Fund's UVBs at just over $3 billion—six
times the prior year's fgure.
Petitioners are four employers who used to contribute to
the Fund. Each withdrew from the Fund between April
and December 2018. Pursuant to § 1391, the Fund assessed
each employer's withdrawal liability “as of ” December 31,
2017 (the last day of the plan year preceding the year in
which they withdrew). The Fund applied the 6.50% dis-
count rate adopted in January 2018 to calculate their with-
drawal liability. Using the 6.50% discount rate, as compared
to the previously adopted 7.50% discount rate, dramatically
increased petitioners' withdrawal liability; M&K Employee
Solutions, for example, was assessed withdrawal liability of
around $6.2 million, whereas it would have owed only around
$1.8 million using the prior assumptions.
Petitioners initiated separate arbitrations to challenge
their withdrawal-liability assessments. See § 1401(a). Each
of the arbitrators determined that the assessment was erro-
neous because the Fund had applied actuarial assumptions
adopted after December 31, 2017. Doing so, the arbitra-
tors reasoned, conficted with § 1391's requirement that with-
drawal liability be calculated “as of ” the measurement date.
The arbitrators instead required the Fund to use the actuar-
ial assumptions that were “in effect” on the measurement
date—i. e., the 7.50% discount rate. App. 293 (emphasis de-
leted); see also id., at 26–27, 49, 71.
The Fund sought review of the arbitral awards in Federal
District Court. Three of the actions were consolidated,
while the fourth proceeded separately. In both cases, the
District Courts disagreed with the arbitrators, holding that
actuaries could use assumptions adopted after the measure-
ment date to calculate withdrawal liability. 2022 WL
4534998, *11 (D DC, Sept. 28, 2022); Trustees of the IAM
Nat. Pension Fund v. Ohio Magnetics, Inc., 656 F. Supp. 3d
112, 136–137 (DC 2023).
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Cite as: 608 U. S. 264 (2026) 271
Opinion of the Court
In a consolidated appeal, the Court of Appeals for the D. C.
Circuit affrmed. 92 F. 4th 316, 322 (2024). The court rea-
soned that “requir[ing] an actuary to determine what as-
sumptions to use before the close of business on the measure-
ment date” would confict with Congress's instruction in
§ 1393(a)(1) “that an actuary use its `best estimate' of the
plan's anticipated experience as of the measurement date.”
Id., at 322–323. Accordingly, the court held that actuaries
could adopt assumptions after the measurement date as long
as the assumptions were “based on the body of knowledge
available up to the measurement date.” Id., at 322 (internal
quotation marks omitted).
The D. C. Circuit's decision conficted with a decision of
the Second Circuit, which held that MPPs must adopt their
interest rate assumptions for withdrawal-liability purposes
on or before the measurement date. National Retirement
Fund v. Metz Culinary Mgmt., Inc., 946 F. 3d 146, 152 (2020).
We granted certiorari to resolve this split over when actuar-
ial assumptions may be selected for purposes of calculating
withdrawal liability. 606 U. S. 930, amended 606 U. S. 958
(2025).2 For the reasons that follow, we now hold that with-
drawal liability can be calculated based on actuarial assump-
tions adopted after the measurement date.
II
Two sections of ERISA govern the calculation of with-
drawal liability: §§ 1391 and 1393. Neither requires that
actuarial assumptions be selected on or before the measure-
ment date.
A
Section 1391 lays out the various methods that plans can
use to calculate withdrawal liability. It does not mention
actuarial assumptions at all. Nevertheless, petitioners ask
2 The parties also disputed below whether actuarial assumptions must
be based on only the information available as of the measurement date.
We leave that question for another day.
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272 M & K EMPLOYEE SOLUTIONS, LLC v. TRUSTEES OF
IAM NAT. PENSION FUND
Opinion of the Court
us to identify a deadline for the selection of assumptions
from § 1391's directive that withdrawal liability be calculated
based on the plan's UVBs “as of ” the measurement date.
See, e. g., § 1391(b)(2)(E)(i). But the “as of ” language sets
no such deadline.
Dictionaries defne “as of ” to mean “at the date men-
tioned.” Oxford American Dictionary 34 (1980); see also
Webster's Third New International Dictionary 129 (1976)
(“at or on (a specifc time or date)”). In context, the term is
understood “to assign an event to one time and the recogni-
tion of it to another.” W. Follett, Modern American Usage
41 (rev. ed. 1998). Thus, § 1391's use of “as of ” means two
things. First, the hard data about the plan that feeds the
UVB calculation must be fxed on the measurement date.
Second, and as all agree, the actual UVB calculation can be
performed after the measurement date. For purposes of
this case, then, the key question is whether actuarial as-
sumptions are akin to the facts about the plan that must be
fxed on the measurement date, or whether they are a part
of the UVB calculation itself and can therefore be selected
after the measurement date.
Petitioners argue that actuarial assumptions are factual
inputs into the UVB calculation, much like hard data such as
the number of plan benefciaries. On this view, to comply
with § 1391, the actuarial assumptions must be “frozen” on
the measurement date. Brief for Petitioners 23. In other
words, they say, the actuary must use the assumptions that
are “in effect” on the measurement date—i. e., the assump-
tions most recently adopted before the measurement date—
to value the UVBs. Brief for Petitioners 37.
But petitioners' argument is based on a fawed under-
standing of actuarial assumptions. These assumptions are
not factual inputs. Instead, they are predictive judgments
about a plan's anticipated future performance—tools actuar-
ies use to calculate the plan's UVBs. The distinction be-
tween tool and fact is clear from the text of ERISA: Section

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Cite as: 608 U. S. 264 (2026) 273
Opinion of the Court
1393 groups actuarial assumptions together with “methods”
in prescribing how withdrawal liability must be calculated.
See § 1393(a)(1). The relevant similarity between assump-
tions and methods is that both are tools used to make actuar-
ial valuations. See, e. g., § 1393(a) (referring to actuarial
assumptions as something “used” to determine UVBs);
§ 1401(a)(3)(B)(i) (same).
The Actuarial Standards of Practice likewise support our
conclusion that actuarial assumptions are not observable
facts about the plan that are “in effect” on a particular date.3
These professional guidelines instruct actuaries to select as-
sumptions for the purpose of making a particular calculation
or measurement. See ASOP No. 27, § 3.3 (“The actuary
should identify the types of assumptions to use for a specifc
measurement,” taking into account, among other things, “the
purpose of the measurement”); id., § 3.8 (“The actuary should
take into account the purpose of the measurement as a pri-
mary factor in selecting a discount rate”). In other words,
actuaries make assumptions when the need for an actuarial
valuation arises.
In this case, for example, the Fund's actuary adopted as-
sumptions for purposes of its 2016 Plan Year annual valua-
tion. The Fund then adopted new actuarial assumptions for
purposes of calculating withdrawal liability for employers
who withdrew in 2018, and later for its 2017 Plan Year annual
valuation. As this case illustrates, actuarial assumptions
are adopted for the purpose of a particular calculation or
measurement; they are not generally “in effect” in the way
that petitioners urge.
With this understanding of actuarial assumptions, peti-
tioners' proposed interpretation of § 1391 falls apart. Be-
3 Consulting the Actuarial Standards of Practice is appropriate here be-
cause this is a statute “addressed to specialists,” so it “must be read by
judges with the minds of the specialists.” Becerra v. Empire Health
Foundation, for Valley Hospital Medical Center, 597 U. S. 424, 434 (2022)
(internal quotation marks omitted).
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274 M & K EMPLOYEE SOLUTIONS, LLC v. TRUSTEES OF
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Opinion of the Court
cause actuarial assumptions are tools used to calculate UVBs
rather than hard data about the plan, they cannot be “frozen”
on the measurement date. Section 1391's “as of ” require-
ment sets the reference point for the factual inputs into the
UVB calculation. It has no bearing on when actuaries must
select the tools, including assumptions, they use to calculate
a plan's UVBs.
B
Section 1393, the section of ERISA that governs the use
of actuarial assumptions for assessing withdrawal liability,
confrms that the measurement date is not a deadline by
which actuaries must select their assumptions. Indeed,
§ 1393 provides no deadline at all. The statute merely
says that the actuary's assumptions must be “reasonable,”
must “tak[e] into account the experience of the plan and rea-
sonable expectations,” and must “offer the actuary's best
estimate of anticipated experience under the plan. ”
§ 1393(a)(1). We generally do not read limitations into stat-
utes that do not appear in their text, Romag Fasteners, Inc.
v. Fossil Group, Inc., 590 U. S. 212, 215 (2020), and we dis-
cern no basis for doing so here.
The omission of any deadline in § 1393 is signifcant given
Congress's inclusion of a similar deadline in a different sec-
tion of the statute. Specifcally: The amortization period for
an employer's withdrawal-liability payments must be deter-
mined based on “the assumptions used for the most recent
actuarial valuation for the plan.” § 1399(c)(1)(A)(ii). But
Congress imposed no similar limit for the actuarial as-
sumptions used to calculate withdrawal liability; we presume
this omission is intentional. See Russello v. United States,
464 U. S. 16, 23 (1983) (“[W]here Congress includes par-
ticular language in one section of a statute but omits it in
another section of the same Act, it is generally presumed
that Congress acts intentionally and purposely in the dis-
parate inclusion or exclusion” (internal quotation marks
omitted)).
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Opinion of the Court
Moreover, § 1393's instruction that actuarial assumptions
refect the actuary's “best estimate of anticipated experience
under the plan,” § 1393(a)(1), supports the conclusion that ac-
tuaries can select their assumptions after the measurement
date. Recall that actuaries choose assumptions based on the
plan's past performance, changes in the market, and other
relevant information. ASOP No. 27, § 3.5. Thus, the as-
sumptions should “refect the actuary's knowledge as of the
measurement date.” Id., § 3.4.6. But the relevant informa-
tion about the plan's performance or macroeconomic condi-
tions, as it stood on the measurement date, may not become
available until after the measurement date. See American
Academy of Actuaries, Issue Brief: Selection of Actuarial As-
sumptions for Multiemployer Plans 4. Requiring actuaries
to use assumptions selected before the measurement date
could therefore prevent them from relying on the most up-
to-date data when selecting their assumptions. This, in
turn, could mean that their assumptions do not refect their
“best estimate.” § 1393(a)(1).
More fundamentally, requiring actuaries to use assump-
tions based on stale data would result in an incoherent statu-
tory scheme. Under petitioners' view, actuaries must value
a plan's UVBs based on hard data as it stood on the measure-
ment date while at the same time applying assumptions se-
lected based on an older set of facts. The statute does not
mandate this mismatch. Instead, actuaries may select their
assumptions after the measurement date in order to value
the UVBs as of the measurement date.
III
Unable to identify a deadline for adopting actuarial as-
sumptions in the text of ERISA, petitioners turn to two
other arguments—one about statutory context and the other
related to policy concerns. Neither has merit.
First, petitioners contend that the statute contains a broad
antiretroactivity principle. They point to a different section
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276 M & K EMPLOYEE SOLUTIONS, LLC v. TRUSTEES OF
IAM NAT. PENSION FUND
Opinion of the Court
of ERISA, § 1394, for support. This section prohibits plans
from applying any new “plan rule or amendment” to an em-
ployer's withdrawal liability if the rule or amendment is
adopted after the employer withdraws. § 1394(a).
But this section hurts rather than helps petitioners. As
they acknowledge, actuarial assumptions are not plan rules
or amendments. Accordingly, the retroactivity limits in
§ 1394 do not apply to actuarial assumptions. Congress
chose not to enact a similar antiretroactivity rule in § 1393,
which strongly suggests that actuarial assumptions are not
subject to any such limitation. See Russello, 464 U. S., at
23. Inferring an antiretroactivity rule for the selection of
actuarial assumptions would override Congress's choice.
So petitioners fall back on a policy argument. They con-
tend that allowing plans to adopt actuarial assumptions after
the measurement date will open the door to manipulation.
Plans and their actuaries, petitioners worry, will retroac-
tively select assumptions in order to increase withdrawing
employers' liability. But their proposed rule—that with-
drawal liability must be based on assumptions adopted be-
fore the measurement date—does nothing to address these
concerns. Plans and actuaries could still select assumptions
with an eye towards infating withdrawal liability before the
measurement date given the signifcant discretion they enjoy
in selecting assumptions.
In any event, “policy concerns cannot trump the best inter-
pretation of the statutory text.” Patel v. Garland, 596 U. S.
328, 346 (2022). Congress chose which limits to impose on
the selection of actuarial assumptions. The statute requires
that actuarial assumptions be “reasonable” and refect actu-
aries' “best estimate.” § 1393(a)(1). And the statute per-
mits employers to challenge actuarial assumptions in arbitra-
tion, including on the ground that they were “unreasonable.”
§ 1401(a)(3)(B)(i). Indeed, many of the worst-case scenarios
petitioners posit—for example, that actuaries will adopt in-
tentionally low discount rates for withdrawal liability but
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Opinion of the Court
high discount rates for other purposes—are subject to chal-
lenge in arbitration. It is not the role of the Court to sup-
plant Congress's choices, as refected in the statutory text,
with our own.
* * *
ERISA does not require pension plans to assess with-
drawal liability based on actuarial assumptions adopted be-
fore the measurement date. We therefore affrm the judg-
ment of the D. C. Circuit.
It is so ordered.
Page Proof Pending Publication

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Page Proof Pending Publication
Reporter’s Note
The attached opinion has been revised to refect the usual publication
and citation style of the United States Reports. The revised pagination
makes available the offcial United States Reports citation in advance of
publication. The syllabus has been prepared by the Reporter of Decisions
for the convenience of the reader and constitutes no part of the opinion of
the Court. Other revisions may include adjustments to formatting, cap-
tions, citation form, and any errant punctuation. The following additional
edits were made:
None

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