Amicus Curiae Brief — M & K Employee Solutions, LLC, et al., Petitioners v. Trustees of the IAM National Pension Fund

Supreme Court briefSep 4, 2025

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No. 23-1209

IN THE

Supreme Court of the United States

————

M&K EMPLOYEE SOLUTIONS, LLC, et al.,

Petitioners,

TRUSTEES OF THE IAM NATIONAL PENSION FUND,

Respondent.

————

On Writ of Certiorari to the

United States Court of Appeals

for the District of Columbia Circuit

————

BRIEF FOR AMICUS CURIAE

JAMES P. NAUGHTON

IN SUPPORT OF PETITIONERS

————

MARK M. TRAPP

Counsel of Record

CONN MACIEL CAREY

53 West Jackson Boulevard

Suite 1352

Chicago, IL 60604

(312) 809-8122

mtrapp@connmaciel.com

Counsel for Amicus Curiae

September 4, 2025

WILSON-EPES PRINTING CO., INC. – (202) 789-0096 – WASHINGTON, D.C. 20002

TABLE OF CONTENTS

Page

TABLE OF AUTHORITIES ................................

INTEREST OF AMICUS CURIAE .....................

SUMMARY OF THE CASE ................................

SUMMARY OF ARGUMENT .............................

ARGUMENT ........................................................

I. Actuarial

Norms

Favor

Fixed

Assumptions to Preserve Predictability ..

II. Post Hoc Assumption Setting Invites

Strategic Behavior and Undermines

Fiduciary Integrity ...................................

III. Potential Post Hoc Adjustments Severely

Undermine Employer Decision-Making ..

IV. ERISA’s Framework Mandates Fixed

Assumptions as of the Measurement

Date ...........................................................

Allowing Post Hoc Assumption Changes

Contradicts ERISA’s Prohibition on

Retroactive Increases and Congress’s

Stated Preference for Predictability ........

VI. Only a Bright-Line Rule Promotes

Predictability and Comports with

Actuarial Standards, Economic Theory,

and Sound Policy.......................................

CONCLUSION ....................................................

(i)

TABLE OF AUTHORITIES

CASES

Page(s)

Bay Area Laundry & Dry Cleaning Pension

Tr. Fund v. Ferbar Corp. of Cal.,

522 U.S. 192 (1997) ................................... 6, 19

Concrete Pipe & Prods. of Cal., Inc. v.

Constr. Laborers Pension Tr. for S. Cal.,

508 U.S. 602 (1993) ............................... 9, 12, 17

Nat’l Ret. Fund v. Metz Culinary Mgmt., Inc.,

946 F.3d 146

(2d Cir.2020) ....... 3, 4, 7, 8, 12, 14, 16-18, 20-23

Trs. of the IAM Nat’l Pension Fund v.

M&K Emp. Sols., LLC,

92 F.4th 316

(D.C. Cir.2024) ......................... 2-4, 7, 12, 14, 16

STATUTES AND REGULATIONS

26 U.S.C. § 430(g)(2)(A) ................................

29 U.S.C. § 1381(b)(1)...................................

29 U.S.C. § 1389 ...........................................

29 U.S.C. § 1391 ................................... 3, 4, 16, 18

29 U.S.C. § 1391(b)(2)(A) ........................... 2, 6, 17

29 U.S.C. § 1391(b)(2)(A)(ii) .........................

29 U.S.C. § 1391(b)(2)(E)(i) ......................... 11, 16

29 U.S.C. § 1391(b)(4)(B)(ii) .........................

29 U.S.C. § 1391(c)(5) ...................................

29 U.S.C. § 1394 ........................................... 18, 20

29 U.S.C. § 1394(a) .......................................

29 U.S.C. § 1399 ...........................................

iii

TABLE OF AUTHORITIES—Continued

Page(s)

29 U.S.C. § 1399(c)(1)(A)(ii) ......................... 13, 16

29 U.S.C. § 1399(c)(1)(B) .............................

29 U.S.C. § 1399(c)(2) .................................. 6, 19

29 U.S.C. § 1399(c)(5) ...................................

29 U.S.C. § 1400 ..........................................

29 U.S.C. § 1400(a) ......................................

29 U.S.C. § 1400(b) ......................................

29 U.S.C. § 1400(c) ......................................

29 U.S.C. § 1401(b)(1) .................................. 6, 19

29 U.S.C. § 1405 ...........................................

American Rescue Plan Act of 2021, Pub. L.

No. 117-2, § 9704, 135 Stat. 4, 185–94 .....

29 C.F.R. pt. 4262.4(b) .................................

29 C.F.R. pt. 4262.16(f) ................................ 7, 13

COURT FILINGS

Br. for Amicus Curiae Chamber of Com. of

the U.S. in Support of Petitioners, M&K

Emp. Sols., LLC v. Trs. of the IAM

Pension Fund, No. 23-1209 (U.S. June

12, 2024) ....................................................

Br. for Appellants, Trs. of the IAM Nat’l

Pension Fund v. M&K Emp. Sols., LLC,

Nos. 22-7157 & 22-7158 (D.C. Cir. Feb.

22, 2023) ....................................................

TABLE OF AUTHORITIES—Continued

Page(s)

Br. for the United States as Amicus Curiae,

M&K Emp. Sols., No. 23-1209 (U.S. May

27, 2025) ....................................................

5, 8

Br. in Opp’n, M&K Emp. Sols., LLC v. Trs.

of the IAM Nat’l Pension Fund, No. 231209 (U.S. July 12, 2024)..........................

5, 8

Br. of Amici Curiae Joseph Abboud Mfg.

Corp. & Waterford Hotel Grp., Inc. in

Support of Def.-Appellant, Nat’l Ret. Fund

v. Metz Culinary Mgmt., Inc.. 946 F.3d

146 (No. 17-1211-cv) (2d Cir. Aug. 1,

2017) ..........................................................

Br. of Amici Curiae The Segal Group,

Milliman, Horizon Actuarial & Cheiron,

Trs. of the IAM Nat’l Pension Fund v.

M&K Emp. Sols., LLC, Nos. 22-7157 &

22-7158 (D.C. Cir. Mar. 30, 2023) ...... 5, 6, 8, 10

OTHER AUTHORITIES

Special Financial Assistance by PBGC, 87

Fed. Reg. 40968 (July 8, 2022) ................. 7, 13

Actuarial

Standards

Bd.,

Actuarial

Standard of Practice No. 27: Selection of

Economic Assumptions for Measuring

Pension Obligations (rev. June 2020)

[ASOP No. 27] .......................................... 6, 9-11

Edward L. Glaeser & Andrei Shleifer, The

Rise of the Regulatory State, 41 J. Econ.

Literature 401 (2003) ................................

TABLE OF AUTHORITIES—Continued

Page(s)

Jill E. Fisch, Retroactivity and Legal

Change: An Equilibrium Approach, 110

Harv. L. Rev. 1055 (1997) .........................

Louis Kaplow, Rules Versus Standards: An

Economic Analysis, 42 Duke L.J. 557

(1992) ................................................. 5, 8, 15, 21

S. 1076, The Multiemployer Pension Plan

Amendments Act of 1980: Summary and

Analysis of Consideration, 96th Cong., 2d

Sess. (Comm. Print 1980) ......................... 18, 19

INTEREST OF AMICUS CURIAE 1

Amicus curiae, James P. Naughton, is a Fellow of

the Society of Actuaries and an Associate Professor

at the University of Virginia’s Darden School of

Business, where he teaches and researches in the

areas of accounting, law, and pension regulation.

He previously worked as an actuarial consultant at

Hewitt Associates LLC, advising multiemployer and

corporate pension plans on valuation, funding, and

regulatory compliance. He holds a Doctor of Business

Administration from Harvard Business School and a

Juris Doctor, cum laude, from Harvard Law School.

Professor Naughton has testified as an expert before

Congress on issues related to multiemployer pension

plans and has published extensively in leading

academic journals on the interaction between pension

accounting, regulatory policy, and financial reporting.

His work examines how actuarial assumptions, legal

frameworks, and governance structures influence

decision-making in pension systems — precisely the

interplay at issue in this case.

He submits this brief to assist the Court in

interpreting ERISA’s timing requirements for withdrawal

liability in a manner consistent with sound actuarial

practice, economic efficiency, and the statute’s commitment to predictability and fairness.

Pursuant to Supreme Court Rule 37.6, amicus curiae states

that no counsel for a party authored this brief in whole or in part,

and no party or counsel for a party made a monetary contribution

intended to fund the preparation or submission of this brief.

Amicus further declares that he has not represented any of the

parties in any capacity in connection with this matter and has no

direct or indirect financial interest in the outcome of the case.

SUMMARY OF THE CASE

Congress enacted the Multiemployer Pension Plan

Amendments Act of 1980 (MPPAA) to prevent employers from avoiding their share of pension obligations

by withdrawing from underfunded multiemployer

plans.2 Under the MPPAA, an employer that ceases

to contribute to a multiemployer plan must pay

withdrawal liability, an obligation that is derived from

its proportionate share of the plan’s unfunded vested

benefits determined as of the end of the plan year

preceding the plan year in which the employer

withdraws.3 The calculation depends heavily on

actuarial assumptions, particularly the discount rate

used to convert expected future benefit payments into

present value.

The case before this Court arises from the D.C.

Circuit’s decision in Trs. of the IAM Nat’l Pension Fund

v. M&K Employee Solutions, LLC, 92 F.4th 316 (D.C.

Cir. 2024). In M&K, several employers, including M&K

Employee Solutions, withdrew during the 2018 plan

year from the IAM National Pension Fund.4 The

Fund’s actuary had long used a 7.5% discount rate for

both withdrawal liability and minimum funding

purposes.5 However, after the statutory measurement

date of December 31, 2017, the Fund’s actuary,

Cheiron, Inc., lowered the discount rate to 6.5% only

for purposes of determining withdrawal liability, while

continuing to use the 7.5% rate for funding purposes.6

See 29 U.S.C. § 1391(b)(2)(A).

Id. at 319.

Id.

Id. at 319–20.

The employers had previously received withdrawal

liability estimates calculated using the 7.5% rate.7

Applying the lower 6.5% rate after the fact substantially increased the assessed withdrawal liabilities.8

The D.C. Circuit upheld the use of the 6.5% discount

rate, holding that actuaries may adopt assumptions

after the measurement date, so long as those

assumptions are based on information as of that date.9

This holding directly conflicts with the Second

Circuit’s earlier decision in Nat’l Ret. Fund v. Metz

Culinary Mgmt., Inc., 946 F.3d 146 (2d Cir. 2020).

In Metz, Metz Culinary Management, Inc. withdrew

during the 2014 plan year from the National

Retirement Fund. The Fund’s actuary had long used a

7.25% discount rate for both withdrawal liability and

minimum funding purposes.10 However, after the

statutory measurement date of December 31, 2013, the

Fund’s newly hired actuary, Horizon Actuarial

Services, LLC, lowered the discount rate to 3.25% only

for purposes of determining withdrawal liability,

while continuing to use the 7.25% rate for funding

purposes.11 Metz had previously received withdrawal

liability estimates calculated using the 7.25% rate.12

The lower discount rate tripled Metz’s assessed

withdrawal liability.13 The Second Circuit held that

§ 1391’s timing provision requires actuarial assumptions to be in place by the measurement date, thus

Id. at 319.

Id. at 320.

Id. at 320–21.

Id.

Id. at 148–49, 151.

Id. at 148.

Id. at 148–49.

eliminating the possibility of retroactive assumption

changes for withdrawal liability purposes.14

The fact that Horizon continued to use a 7.25% rate

for minimum funding purposes raised concerns about

how two dramatically different discount rates (3.25%

versus 7.25%) could simultaneously reflect a best

estimate of the same underlying construct—the longterm expected return on the Fund’s pension assets.15

This inconsistent application was a central concern of

the Second Circuit, which recognized the potential for

opportunistic manipulation by the Fund through its

actuary.16

The D.C. Circuit did not follow Metz, thereby

creating a clear circuit split on the meaning of ERISA’s

fixed-date rule. The petitioners in M&K now seek

resolution of that conflict.

SUMMARY OF ARGUMENT

This case presents a fundamental question of statutory

interpretation with profound actuarial and economic

implications: whether a multiemployer pension plan

may calculate withdrawal liability using actuarial

assumptions adopted after the statutory measurement.

Petitioners have consistently argued that § 1391’s

direction to calculate withdrawal liability as of the end

of the plan year requires actuarial assumptions to

be fixed as of that statutory date.17 This brief does

not restate those statutory arguments. Instead, it

Id. at 152.

Id. at 151–52.

Id. at 151.

See Br. for Appellants at 17–24, Trs. of the IAM Nat’l Pension

Fund v. M&K Emp. Sols., LLC, Nos. 22-7157 & 22-7158 (D.C. Cir.

Feb. 22, 2023).

supports them by explaining, from an actuarial

and economic perspective, why post-measurementdate adjustments neither improve accuracy nor

comport with sound policy, and why ERISA’s fixed-date

rule is the only framework consistent with actuarial

standards and efficient regulatory design.

At each stage of this litigation, post-measurement

date assumption setting has been defended in the

name of “accuracy”: by the Fund in its opposition to

certiorari,18 by actuarial firms as amici in the D.C.

Circuit,19 and by the Solicitor General, who urged this

Court to grant review but nonetheless endorsed the

D.C. Circuit’s interpretation.20 Yet none of these parties

present empirical evidence that post-measurementdate changes improve accuracy, and in actuarial

practice, “perfect hindsight” is neither attainable nor

the relevant standard.

In liability measurement, especially for statutory

debt as consequential as withdrawal liability, predictability, not retroactive recalibration, is the guiding

principle.21 Employers make withdrawal decisions

based on liability estimates provided before the

statutory date and Congress fixed that date to ensure

Brief in Opp’n at 4–8, M&K Emp. Sols., LLC v. Trs. of the IAM

Nat’l Pension Fund, No. 23-1209 (U.S. July 12, 2024).

Brief of Amici Curiae The Segal Group, Milliman, Horizon

Actuarial & Cheiron at 7–9, Trs. of the IAM Nat’l Pension Fund v.

M&K Emp. Sols., LLC, Nos. 22-7157 & 22-7158 (D.C. Cir. Mar. 30,

2023).

Brief for the United States as Amicus Curiae at 8–13, M&K

Emp. Sols., No. 23-1209 (U.S. May 27, 2025).

See Louis Kaplow, Rules Versus Standards: An Economic

Analysis, 42 Duke L.J. 557, 562–63 (1992) (explaining that rules

provide stable ex ante guidance in high-information-asymmetry

environments).

those estimates would match the assumptions ultimately

used in the assessment.22 When a plan has the ability

to change its assumptions after the employer has

acted, the employer is being forced to make a critical

business decision in the dark, and under ERISA’s “pay

now, dispute later” regime23 must immediately pay

potentially inflated amounts it could not possibly have

foreseen.24

In their D.C. Circuit amicus brief,25 the actuarial

firms defend post hoc flexibility without citing any

legal authority, regulatory endorsement, or empirical

evidence that supports the use of retroactive assumptionsetting in this context. Rather, they claim support from

Actuarial Standard of Practice No. 27 (ASOP No. 27).

But ASOP No. 27 is aimed at forward-looking funding

and accounting valuations, not backward-looking

withdrawal liability determinations.26 Moreover, ASOP

No. 27 cannot override ERISA’s statutory command.

Indeed, the best evidence of legislative intent for

permissible actuarial discretion in the multiemployer

pension plan setting lies in the PBGC’s administration

See 29 U.S.C. § 1391(b)(2)(A).

See 29 U.S.C. § 1401(b)(1); Bay Area Laundry & Dry Cleaning

Pension Tr. Fund v. Ferbar Corp. of Cal., 522 U.S. 192, 208–09 (1997).

See 29 U.S.C. § 1399(c)(2)(“Withdrawal liability shall be

payable in accordance with the schedule set forth by the plan

sponsor… notwithstanding any request for review or appeal of

determinations of the amount of such liability or of the schedule.”).

Brief of Amici Curiae The Segal Group, Inc., Milliman, Inc.,

Horizon Actuarial Services, LLC, and Cheiron, Inc. at 6–9, Trs. of

the IAM Nat’l Pension Fund v. M&K Employee Solutions, LLC,

Nos. 22-7157 & 22-7158 (D.C. Cir. Mar. 30, 2023).

See Actuarial Standards Bd., Actuarial Standard of Practice

No. 27: Selection of Economic Assumptions for Measuring Pension

Obligations § 1.2 (rev. June 2020) [hereinafter ASOP No. 27]

(scope: pension measurements, primarily funding and accounting).

of the Special Financial Assistance program, which

mandates the use of fixed assumptions, thus prohibiting selective or retroactive adjustments to avoid

precisely this kind of opportunism.27

The Second Circuit’s decision in Metz recognized

that post-measurement-date assumption changes invite

gamesmanship and create economic uncertainty.28

From an actuarial perspective, such changes provide

no meaningful improvement in accuracy. In both M&K

and Metz, the post-measurement discount rate

changes could just as easily have been adopted before

year-end,29 confirming that the retroactive change did

not improve accuracy. The M&K rule thus introduces

uncertainty and the risk of opportunism without any

corresponding gain in precision. By contrast, the

Metz rule secures predictability while preserving

accuracy. That balance makes Metz a better approach

on actuarial and economic dimensions. Metz also

correctly harmonizes ERISA’s timing and reasonableness provisions, enforcing the statute’s structural

commitment to predictability, neutrality, and fairness.

This Court should adopt Metz and reaffirm that

withdrawal liability must be calculated using the

assumptions in effect on the statutory measurement

date. Such a rule is consistent with actuarial practice,

economic theory, and sound policy, and it ensures that

See 87 Fed. Reg. 40968, 40995–96 (July 8, 2022) (codified at

29 C.F.R. § 4262.16(f)).

See Nat’l Ret. Fund v. Metz Culinary Mgmt., Inc., 946 F.3d

146, 151–52 (2d Cir. 2020) (noting that selective changes in

assumptions create a “risk of bias” and are “presumptively

unreasonable”).

Id. at 148–49, 151–52 (noting that the discount rate switch

was to a published PBGC rate, a benchmark that is determined

by the PBGC not the plan).

critical business decisions are not

uncertainty and post hoc opportunism.

subject

ARGUMENT

I. Actuarial Norms Favor Fixed Assumptions

to Preserve Predictability

The principal opponents of the Metz rule—including

the Fund, the Solicitor General, and actuarial amici—

have all defended an approach under which actuaries

may adopt assumptions after the measurement date,

so long as those assumptions are derived from data

in existence on the measurement date.30 The primary

justification for this approach is the assertion

that post-measurement assumption changes enhance

accuracy. This belief is unwarranted on two counts.

First, while accuracy is always desirable, predictability, not accuracy, is the guiding principle when it

comes to the determination of withdrawal liability.

Legal rules that allow regulated parties to plan and

act in reliance on known standards are more valuable

than rules that introduce uncertainty.31 Courts and

See Brief in Opp’n at 4–8, M&K Emp. Sols., LLC v. Trs. Of

the IAM Nat’l Pension Fund, No. 23-1209 (U.S. July 12, 2024)

(arguing that actuarial accuracy requires the ability to

incorporate year-end data after the measurement date); Brief for

the United States as Amicus Curiae at 8–13, M&K Emp. Sols.,

No. 23-1209 (U.S. May 2025) (endorsing the D.C. Circuit’s rule

that assumptions may be set post-measurement date if based on

data “as of” that date); Brief of Amici Curiae Segal Group,

Milliman, Horizon Actuarial & Cheiron at 7–9, Trs. of the IAM

Nat’l Pension Fund v. M&K Emp. Sols., LLC, Nos. 22-7157 & 227158 (D.C. Cir. Mar. 30, 2023) (asserting that actuarial standards

contemplate post-date assumption selection in order to achieve

more accurate “best estimates”).

See Kaplow, supra note 21, at 562–63 (explaining that rules

enhance predictability in settings with asymmetric information).

economists alike have recognized this point: in

environments characterized by asymmetrical incentives

and opaque calculations, bright-line rules are essential.

They promote neutrality, discourage opportunism, and

reduce litigation.32

In fact, complete accuracy is unobtainable when

it comes to actuarial calculations, which are, by

their nature, estimates rather than prophecies. They

necessarily rest on assumptions about uncertain

future events: when participants will retire, how long

they will live, the investment returns the plan’s assets

will generate, and countless other variables.33 No one

supposes that the actuary’s projections will match the

future with perfect fidelity. When reality diverges from

prior expectations, the original estimate is not

retroactively rewritten. The estimate serves its

purpose at the time it is made: to provide a consistent,

reasonable basis for planning and decision-making at

a point in time, not to guarantee the future.34

Second, it is actuarially and economically implausible that the discount rate assumption, which reflects

long-term expected returns measured over decades,

would materially change based on events that occur

before but are not known until after plan year-end.

Even significant capital market shifts, which are

See Concrete Pipe & Prods. of Cal., Inc. v. Constr. Laborers

Pension Tr. for S. Cal., 508 U.S. 602, 633 (1993) (noting potential

for bias in withdrawal liability calculations).

See Id. at 635–36 (“Imprecision inheres in the choice of

actuarial methods and assumptions.”).

See ASOP No. 27, supra note 26, § 3.12.3 (instructing

actuaries to focus on long-term patterns, not “recent experience”

or “short-term fluctuations in economic or demographic data”).

observable prior to plan year-end, rarely alter a wellfounded long-term projection. Actuarial standards of

practice, including the ASOP No. 27 extensively cited

by the actuarial firms in their amicus brief to the

D.C. Circuit, emphasize gradual adjustments based on

broad patterns, not immediate events.35 The residual

year-end data that becomes available only after the

close of the plan year is, at most, marginal. To suggest

that such data must be incorporated post hoc to

maintain “best estimate” standards grossly overstates

the role of such data and completely misrepresents the

nature of long-term return assumptions and the

nature of actuarial assumption setting.36

In their amicus brief to the D.C. Circuit, the

actuarial firms also suggest that ASOP No. 27

supports post hoc assumption changes in the context

of withdrawal liability calculations.37 It does not.

ASOP No. 27 was not written to address specific issues

See ASOP No. 27, supra note 26, §§ 3.9, 3.12, 3.12.3–.4

(directing actuaries to base assumptions on long-term

expectations and patterns rather than short-term fluctuations,

and to avoid abrupt, inconsistent changes absent good reason).

Id. § 3.12 (“In selecting a reasonable assumption, the actuary

should consider the purpose of the measurement, the length of

the measurement period, and relevant data, giving more weight

to long-term expectations…The actuary should focus on patterns

and trends rather than giving undue weight to recent, temporary

economic fluctuations.”).

See Brief of Amici Curiae The Segal Grp., Inc., Milliman, Inc.,

Horizon Actuarial Servs., LLC & Cheiron, Inc. at 8–9, Trs. of the

IAM Nat’l Pension Fund v. M&K Emp. Sols., LLC, Nos. 22-7157 &

22-7158 (D.C. Cir. Mar. 30, 2023).

that arise in the determination of withdrawal liability.38

Rather, ASOP No. 27 was developed primarily for

defined benefit pension plan estimates generated for

funding valuations, accounting disclosures, and cash

flow projections for ongoing plans.39 These types of

measurements are inherently forward-looking and

often involve post-measurement date assumption

selection, especially for public pension plan funding,

where annual valuations are conducted long after the

valuation date.

By contrast, withdrawal liability under ERISA

Section 4211 is a backward-looking liability determination triggered by a specific legal event — an

employer’s withdrawal — that must be calculated as

of the last day of the prior plan year.40 Thus,

withdrawal liability is a unique, statutorily defined

debt, not a funding target or a budget. Its estimation

is fundamentally different than the type of valuation

that ASOP No. 27 addresses.

II. Post Hoc Assumption Setting Invites

Strategic Behavior and Undermines

Fiduciary Integrity

Allowing for post hoc assumption changes provides

an opportunity for the Fund to pressure its actuary to

conform with the Fund’s preferences and to face

possible replacement if the actuary does not conform.

It is a step too far to assume that actuaries are

Withdrawal liability is never mentioned in ASOP No. 27

nor in the accompanying appendices providing background on

current practices and comments on the Second Exposure Draft

and responses.

See ASOP No. 27, supra note 26, § 1.2 (scope: pension

measurements, primarily funding and accounting).

29 U.S.C. § 1391(b)(2)(E)(i).

immune from client pressure, as the records in both

M&K and Metz clearly demonstrate. In Metz, a newly

hired actuary adopted a much lower discount rate only

for withdrawal liability purposes after the statutory

measurement date.41

In Metz, the application of a significantly lower

discount rate only in the context of withdrawal

liability—and not for plan solvency or contribution

calculations—reveals a strategic asymmetry that the

Second Circuit appropriately viewed as incompatible

with ERISA’s requirement for consistent, reasonable

estimates.42 After all, both the 3.25% and 7.25%

discount rate assumptions reflect the same economic

construct—the long-term expected return on the

Fund’s pension assets.43

To be clear, this is not a challenge to the integrity

of the actuarial profession as a whole. Actuaries

frequently act in good faith and provide essential

guidance to complex retirement systems. But deference to actuarial discretion must have limits,

See M&K, 92 F.4th at 320–21; Metz, 946 F.3d at 148–49, 151–

52.

Metz, 946 F.3d at 148–49, 151–52. (noting that use of a

significantly lower discount rate solely for withdrawal liability

calculations, and not for funding or other purposes, “illustrates

the type of results that can be ‘attacked as presumptively

unreasonable’” under Concrete Pipe).

Notably, there is no evidence in the Metz record that the plan

invested the additional withdrawal liability collections using the

more conservative asset allocation implied by the lower discount

rate. To the contrary, the plan continued using the higher 7.25%

rate for its own funding valuations, indicating that it maintained

a portfolio consistent with higher expected returns and greater

risk exposure.

especially where incentives are misaligned and the

legal framework provides specific timing constraints.

The Pension Benefit Guaranty Corporation (PBGC)

has recognized the risks of discretionary actuarial

assumptions, especially in high-stakes settings where

liability determinations are susceptible to manipulation. In the Special Financial Assistance (SFA)

Program created under the American Rescue Plan Act

of 2021, Pub. L. No. 117-2, § 9704, 135 Stat. 4, 185–94,

actuaries were required to generate projections based

on the interest rate used in the plan’s most recent zone

certification for non-SFA assets and the PBGC’s part

4044 discount rate for SFA assets. These prescriptions

eliminated selective or retroactive adjustments to the

discount rate.44 This choice echoes ERISA’s own

structure, which directs that withdrawal liability

installment payments be based on “the assumptions

used for the most recent actuarial valuation.”45

These constraints reflect a deliberate policy decision

to limit discretion in favor of predictability, integrity,

and fairness.46 With the SFA, the PBGC’s decision to

impose these limits affirms the broader point: when

liabilities are large and incentives are misaligned,

bright-line standards are essential to preserve integrity and fairness.

See 87 Fed. Reg. 40968, 40995–96 (July 8, 2022) (codified at

29 C.F.R. § 4262.16(f)).

29 U.S.C. § 1399(c)(1)(A)(ii).

See 29 C.F.R. § 4262.4(b) (requiring use of standardized

interest rate assumptions for SFA eligibility).

III. Potential Post Hoc Adjustments Severely

Undermine Employer Decision-Making

Only Metz’s reasoning—requiring assumptions to be

fixed as of the measurement date—allows an employer

to withdraw from a plan with confidence that its

withdrawal liability will line up with prior estimates.47

Without this requirement, any estimate provided prior

to withdrawal becomes speculative as plans retain

the ability to materially alter assumptions after

the employer has acted. This concern applies equally

to the D.C. Circuit’s rule in M&K, which permits

actuaries to adopt assumptions after the measurement date so long as they are based on information as

of that date.48 Even under that more moderate

formulation, employers cannot know whether or when

assumptions will be changed. Any discretion left in

the hands of plans or their actuaries after the

measurement date creates the potential for strategic

recalibration and makes it impossible for employers to

rely on liability estimates at the time they make the

withdrawal decision.

This is not a hypothetical concern. In their amicus

brief in Metz, employers such as Joseph Abboud

Manufacturing and Waterford Hotel Group explained

that they relied on pre-withdrawal estimates based on

long-standing assumptions, only to have those

assumptions changed retroactively, causing their

withdrawal liability to skyrocket.49 These cases

See Metz, 946 F.3d at 148–49, 151–52. (holding that interest

rate assumptions “must be determined as of the last day of the

plan year preceding the employer’s withdrawal”).

See M&K, 92 F.4th at 320–21.

See Brief of Amici Curiae Joseph Abboud Mfg. Corp. &

Waterford Hotel Grp., Inc. in Support of Def.-Appellant at 6–8,

Metz Culinary Mgmt., 946 F.3d 146 (No. 17-1211-cv) (2d Cir. Aug.

exemplify the legal and economic instability inherent

in permitting plans to alter the financial terms after

an employer has already decided to exit.

Retroactive recalibration also violates basic tenets

of legal and economic design. Legal rules are meant to

provide forward-looking guidance so that regulated

actors can plan their conduct accordingly.50 Scholars

have emphasized that retroactive rule changes impose

efficiency costs by distorting ex ante behavior and

creating legal uncertainty.51 When actors cannot rely

on the legal framework to remain stable through the

course of a transaction, their incentive to engage in

productive activity diminishes. Employers are entitled

to shape their business conduct—such as whether and

how to withdraw from a multiemployer plan—based

on the law and assumptions reasonably in place at the

time. Allowing plan actuaries to revise those assumptions months later, and apply them retroactively,

collapses this reliance structure and undermines

economic incentives.

IV. ERISA’s Framework Mandates Fixed

Assumptions as of the Measurement Date

ERISA’s withdrawal liability regime is anchored by

a fixed statutory measurement date which governs not

only the timing of the valuation but also the inputs

used to calculate liability. This design ensures that

1, 2017) (describing reliance on prior estimates and subsequent

retroactive change in discount rate).

See Kaplow, supra note 21, at 562–63 (explaining efficiency

advantages of rules that provide stable ex ante guidance).

See Jill E. Fisch, Retroactivity and Legal Change: An

Equilibrium Approach, 110 Harv. L. Rev. 1055, 1060–61 (1997)

(explaining that retroactivity undermines reliance and increases

uncertainty).

employer exposure is based on settled assumptions

rather than discretionary adjustments made after

withdrawal. Section 1391(b)(2)(A)(ii) includes in the

calculation unfunded vested benefits, the starting

point in the withdrawal liability determination, only

for years ending “before the plan year in which the

withdrawal of the employer occurs,”52 while § 1381(b)(1)

reinforces this fixed date by tying withdrawal liability

directly to the plan’s “unfunded vested benefits”

as determined under § 1391. Section 1399(c)(1)(A)(ii)

additionally directs that withdrawal liability installment payments be based on “the assumptions used for

the most recent actuarial valuation.” Together, these

provisions make clear that both the withdrawal

liability and the assumptions used to calculate it are

fixed as of the measurement date.

The Second Circuit in Metz correctly interpreted

this framework to require that actuarial assumptions

must not only rely on pre-existing data but must be

formally adopted as-of the measurement date. Allowing

post hoc changes disrupts this scheme by injecting

retroactive discretion into a statutory regime that was

designed for predictability. As that court noted, absent

a statutory basis for retroactive assumption-setting,

the default rule is continuity: assumptions from the

prior plan year should roll forward.53 The D.C. Circuit’s

contrary reading renders the timing clause in § 1391

effectively meaningless.54

See also § 1391(b)(2)(E)(i) (proportional share measured “as

of the end of the plan year preceding” the withdrawal).

Metz, 946 F.3d at 149–50.

See M&K, 92 F.4th at 320–21 (holding that assumptions may

be adopted after the measurement date if based on information

available “as of” that date).

The approach in Metz is supported by the fact that

ERISA explicitly identifies circumstances where

retroactive adjustments to withdrawal liability are

permitted. For example, § 1391(b)(4)(B)(ii) allows funds

to reallocate amounts that prove uncollectible because

of the de minimis rule,55 the 20-year cap on payments,56 or

the insolvency limitation.57 Congress thus distinguished

between post hoc reallocations for collection shortfalls,

which it expressly authorized, and post hoc recalibration of assumptions, which it did not.

The approach in Metz better aligns with ERISA’s

broader valuation architecture, which clearly distinguishes between forward-looking and backward-looking

financial calculations. For example, for minimum

funding determinations, 26 U.S.C. § 430(g)(2)(A) states

that “the valuation date of a plan for any plan year

shall be the first day of the plan year,” thus enabling

timely contribution decisions. Withdrawal liability, by

contrast, is a retrospective assessment, rooted in the

financial condition of the plan at the end of the prior

year.58 Permitting assumption changes after the

measurement date would collapse this distinction

between forward- and backward-looking valuations. It

would allow plans to recalculate liabilities using

information and methods that were not in use—and

perhaps not even contemplated—at the relevant time.59

In sum, ERISA’s text, structure, and design converge

on the same point: withdrawal liability must be

29 U.S.C. § 1389.

29 U.S.C. § 1399(c)(1)(B).

29 U.S.C. § 1405.

See 29 U.S.C. § 1391(b)(2)(A).

Concrete Pipe, 508 U.S. at 633 (recognizing the dangers of

discretionary assumption changes in withdrawal liability).

determined using assumptions fixed as of the statutory measurement date. Section 1381 ties liability to

unfunded vested benefits; § 1391 fixes the unfunded

vested benefits determination to be before the plan

year in which the withdrawal occurs; § 1399 directs

that withdrawal liability installment payments be

based on “the assumptions used for the most recent

actuarial valuation”; and § 1394 shows that when

Congress intended post-withdrawal changes, it explicitly said so. The Second Circuit’s rule in Metz honors

this cohesive framework by ensuring that liability

determinations are anchored to settled assumptions,

just as ERISA requires. The D.C. Circuit’s contrary

approach strips the timing clause of meaning, injects

discretion after the fact, and undermines the statute’s

central commitment to predictability, neutrality, and

fairness.

V. Allowing Post Hoc Assumption Changes

Contradicts ERISA’s Prohibition on Retroactive Increases and Congress’s Stated

Preference for Predictability

The ERISA withdrawal liability framework hinges

on predictability. Congress designed the regime so that

employers could understand their exposure and plan

accordingly. Together, the statutory ceiling on annual

payments and the 20-year maximum payment term

“act[] as a ceiling on the amount of liability that an

employer owes.”60 The Senate Committee added that it

“supports the combination of the 20-year cap with a

periodic payment based on past contributions as a way

of making both the maximum amount of liability and

S. 1076, The Multiemployer Pension Plan Amendments Act

of 1980: Summary and Analysis of Consideration, 96th Cong., 2d

Sess. 18 (Comm. Print 1980).

the annual amount required to be paid toward that

liability easily predictable by employers.”61 Consistent

with that focus on predictability, ERISA enforces a

“pay now, dispute later” regime, requiring employers

to make payments on the schedule imposed by the

plan—even when they challenge the liability calculation in arbitration or litigation.62

As the Supreme Court has recognized, this system

is designed to protect plan liquidity while disputes

are pending.63 Under this regime, if a plan inflates

liability through changes retroactively adopted after

the measurement date, the employer must still pay the

claimed amount during the dispute.64 Nonpayment

can trigger acceleration and enforcement penalties.65

This structure makes it essential that the inputs used

in calculating liability are fixed and knowable at the

time of decision-making.

Because of this structure, plans are prohibited from

increasing withdrawal liability through plan amendments adopted after an employer has withdrawn.66

Congress also imposes strict timing and oversight

requirements on post-MPPAA plan amendments

Id.

See 29 U.S.C. §§ 1399(c)(2), 1401(b)(1).

Bay Area Laundry & Dry Cleaning Pension Tr. Fund v. Ferbar

Corp. of Cal., 522 U.S. 192, 208–09 (1997) (explaining that

Congress required interim payments to “protect plans from the

risk of employer insolvency”).

See 29 U.S.C. § 1399(c)(2) (requiring payment according to

the schedule “notwithstanding any request for review or appeal”).

See 29 U.S.C. § 1399(c)(5) (permitting the plan sponsor, in the

event of default, to accelerate the full outstanding liability with

interest).

See 29 U.S.C. § 1394(a) (prohibiting application of plan

amendments that “increase the amount of unfunded vested benefits”

to employers who withdrew before the amendment’s adoption).

generally. These provisions show that when Congress

intended post-withdrawal changes to be permitted, it

prescribed explicit timing and review safeguards—

underscoring the absence of any comparable authority

for retroactive assumption changes. A prohibition

against assumption changes after the measurement

date would perfectly incorporate the intent of § 1394’s

prohibition on retroactive plan amendments. In both

contexts, ERISA’s prohibition against post hoc changes

to withdrawal liability preserves fairness, transparency,

and accountability.68

VI. Only a Bright-Line Rule Promotes Predictability and Comports with Actuarial

Standards, Economic Theory, and Sound

Policy

The risks of discretionary actuarial changes are not

abstract. As the Chamber of Commerce of the United

States explained in its amicus curiae brief supporting

certiorari in this case, the ability of plans to retroactively alter liability calculations deters employer

participation, invites forum shopping, and destabilizes

bargaining relationships.69 A rule that permits retro-

Section 1400 requires PBGC review of any amendment

adopted more than three years after MPPAA’s effective date; such

an amendment may take effect only if PBGC does not disapprove

it within 90 days. 29 U.S.C. § 1400(a), (c). Amendments altering

withdrawal liability allocation methods are subject to special

procedures under § 1391(c)(5). Id. § 1400(b).

Metz, 946 F.3d at 148–49, 151–52. (warning that retroactive

assumption changes invite bias and undermine statutory safeguards).

See Brief for Amicus Curiae Chamber of Com. of the U.S. in

Support of Petitioners at 6–9, M&K Emp. Sols., LLC v. Trs. of the

IAM Pension Fund, No. 23-1209 (U.S. June 12, 2024) (arguing that

retroactive changes to actuarial assumptions deter employer

active recalibration exposes employers to asymmetric

and unpredictable liabilities, especially in multijurisdictional plans.

Bright-line rules offer an established remedy.

Economic literature has long recognized that brightline rules are preferable in settings where actors face

asymmetric information, high enforcement costs, or

incentives to strategically exploit uncertainty.70 Brightline rules reduce ambiguity and compliance costs,

promote uniform application, and limit the scope for

discretion that can lead to opportunistic behavior.

Rules outperform standards in circumstances requiring

advance planning and predictable guidance, especially

where post hoc evaluation would be costly or subjective.71

Rules also constrain opportunism by self-interested

actors in complex, repeat-play institutional settings.72

In the multiemployer pension context, where plan

trustees and actuaries have informational and

procedural advantages over employers, and where

liability calculations are high-stakes and technical, a

rule-based framework ensures neutrality and

transparency. The Metz rule fits this framework, while

participation in multiemployer plans, promote forum shopping,

and undermine stable collective bargaining).

See Kaplow, supra note 21, at 562–63 (explaining that rules

provide greater predictability and reduce decision costs in highinformation-asymmetry environments).

Id. at 563–65.

See Edward L. Glaeser & Andrei Shleifer, The Rise of the

Regulatory State, 41 J. Econ. Literature 401, 408–10 (2003).

the D.C. Circuit’s open-ended standard invites inconsistent outcomes and discretionary abuse.73

The multiemployer pension system is a textbook

example of a regulatory environment that benefits

from bright-line rules. These plans operate under

collective governance, involve hundreds of employers

and thousands of participants, and frequently span

industries with varying financial health. The complexity

and interconnectedness of the system create enormous

opportunities for discretion and asymmetry in

information and incentives. Trustees and actuaries

often have long-standing relationships, and decisions

are made without centralized oversight. In such an

environment, where the costs of error or manipulation

are borne by others—be it withdrawing employers,

new entrants, or the PBGC—clear, objective rules are

essential to avoid gamesmanship and preserve

confidence in the system.

The fixed measurement date requirement, and the

related limitation on retroactive assumption-setting,

ensure that withdrawal liability is calculated on a

predictable, verifiable, and evenly applied basis. This

approach is not only the most efficient rule, but also

the approach that most closely aligns with actuarial

standards, economic theory, and sound policy design.

See Metz, 946 F.3d 150–52 (warning against the risk of

bias when plan-controlled assumption changes apply only to

withdrawal liability).

CONCLUSION

This case presents an opportunity for the Court to

prioritize clarity and consistency in the administration

of multiemployer pension plans. ERISA establishes a

fixed measurement date to ensure that employers can

make critical decisions based on known rules and

stable assumptions , and actuarial practice confirms

why that bright-line rule is essential. Adopting the

D.C. Circuit’s approach would reintroduce discretionary recalibration and undermine the statutory

framework Congress enacted to protect predictability

and fairness. The Court should instead adopt the

Second Circuit’s rule in Metz. A judicially enforced

bright-line rule requiring plans to use actuarial

assumptions in effect on the measurement date would

not only limit uncertainty and prevent opportunism

without impacting accuracy, but would also reinforce

fiscal discipline in a system that urgently needs it.

Respectfully submitted,

MARK M. TRAPP

Counsel of Record

CONN MACIEL CAREY

53 West Jackson Boulevard

Suite 1352

Chicago, IL 60604

(312) 809-8122

mtrapp@connmaciel.com

Counsel for Amicus Curiae

September 4, 2025

This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.