United Mine Workers of America v. Energy West Mining Company ( 2022 )


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  •  United States Court of Appeals
    FOR THE DISTRICT OF COLUMBIA CIRCUIT
    Argued October 25, 2021                 Decided July 8, 2022
    No. 20-7054
    UNITED MINE WORKERS OF AMERICA 1974 PENSION PLAN, ET
    AL.,
    APPELLEES
    v.
    ENERGY WEST MINING COMPANY,
    APPELLANT
    Appeal from the United States District Court
    for the District of Columbia
    (No. 1:18-cv-01905)
    Yaakov M. Roth argued the cause for appellant. With him
    on the briefs were Sherif Girgis, Gregory J. Ossi, Mark H.M.
    Sosnowsky, and Christopher R. Williams.
    Bryan Killian argued the cause for appellee. With him on
    the brief were John R. Mooney, Paul A. Green, Olga M. Thall,
    and Stanley F. Lechner. Charles P. Groppe entered an
    appearance.
    Before: RAO and WALKER, Circuit Judges, and SENTELLE,
    Senior Circuit Judge.
    2
    Opinion for the Court filed by Circuit Judge RAO.
    RAO, Circuit Judge: The Multiemployer Pension Plan
    Amendments Act (“MPPAA”) requires an employer to pay
    “withdrawal liability” if it decides to leave a multiemployer
    pension plan. Calculating the amount of money the employer
    owes the plan requires an actuary to project the plan’s future
    payments to pensioners. As with any financial projection, this
    requires making assumptions about the future. The MPPAA
    requires the actuary to use “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.” 
    29 U.S.C. § 1393
    (a)(1).
    The Energy West Mining Company (“Energy West”)
    withdrew from the United Mine Workers of America 1974
    Pension Plan (“Pension Plan”) in 2015. In calculating Energy
    West’s withdrawal liability, the actuary did not rely on the
    Pension Plan’s performance to determine what discount rate to
    use, but instead adopted a risk-free discount rate. An arbitrator
    upheld the risk-free discount rate and the district court granted
    summary judgment to the Pension Plan, enforcing the arbitral
    award. We reverse because the actuary’s choice of a risk-free
    rate violates the MPPAA’s command to use assumptions that
    are “the actuary’s best estimate of anticipated experience under
    the plan.”
    I.
    A.
    To ensure that employees who were promised a pension
    would actually receive it, Congress enacted the Employee
    Retirement Income Security Act of 1974 (“ERISA”). See 
    29 U.S.C. § 1001
    (a); Pension Benefit Guar. Corp. v. R. A. Gray &
    3
    Co., 
    467 U.S. 717
    , 720 (1984); see generally Pub. L. No. 93-
    406, 
    88 Stat. 829
     (codified as amended at 
    29 U.S.C. §§ 1001
     et
    seq. and in scattered sections of the Internal Revenue Code).
    By the late 1970s, it had become clear that ERISA was failing
    to stabilize multiemployer pension plans—those maintained
    pursuant to a collective bargaining agreement between multiple
    employers and a union.1 R. A. Gray, 
    467 U.S. at
    721–22; see
    also 
    29 U.S.C. § 1002
    (37)(A) (defining multiemployer plan).
    Like single employer plans, multiemployer plans had to meet
    minimum funding standards, which require employers to
    contribute annually to the plan whatever is needed to ensure it
    has enough assets to pay for the employees’ vested pension
    benefits when they retire. See Milwaukee Brewery Workers’
    Pension Plan v. Jos. Schlitz Brewing Co., 
    513 U.S. 414
    , 416
    (1995). Unlike employers managing a single employer plan,
    however, employers in multiemployer plans could withdraw
    without triggering the plan-termination provisions of ERISA
    and thereby avoiding obligations to make ongoing
    contributions.2
    If a multiemployer plan was financially stable, then
    ERISA worked. But if a plan became financially troubled, large
    contributions would be needed to meet minimum funding
    standards, incentivizing employers to withdraw and
    1
    Multiemployer plans are used mostly in industries where there are
    hundreds or thousands of small employers going in and out of
    business and where the nexus of the employment relationship is the
    union that represents employees who typically work for many of
    those employers over the course of their career. See Concrete Pipe
    & Prods. of Cal., Inc. v. Constr. Laborers Pension Trust for S. Cal.,
    
    508 U.S. 602
    , 606 (1993).
    2
    If an employer withdrew from a plan, the benefits its employees
    earned while the employer was part of the plan would remain on the
    plan’s books.
    4
    precipitating a death spiral for the plan. See 
    id.
     at 416–17.
    Every employer withdrawal would shrink a plan’s contribution
    base, forcing the remaining employers to make even larger
    contributions and increasing their incentive to withdraw.
    ERISA’s only check on this incentive was that if a plan
    terminated within five years of an employer’s withdrawal, that
    employer would be liable for its share of the unfunded vested
    benefits. 
    29 U.S.C. § 1364
     (1976); Milwaukee Brewery
    Workers’ Pension Plan, 513 U.S at 416. Despite this risk,
    however, employers chose to withdraw, causing “a significant
    number of [multiemployer] plans” to experience “extreme
    financial hardship.” R. A. Gray, 
    467 U.S. at 721
    .
    In response, Congress enacted the Multiemployer Pension
    Plan Amendments Act of 1980, Pub. L. No. 96-364, 
    94 Stat. 1208
    . The MPPAA “transformed what was only a risk (that a
    withdrawing employer would have to pay a fair share of
    underfunding) into a certainty” by requiring employers to pay
    “a withdrawal charge” upon their complete or partial
    withdrawal from a plan. Milwaukee Brewery Workers’ Pension
    Plan, 
    513 U.S. at 417
    ; see 
    29 U.S.C. § 1381
    (a). Specifically, a
    withdrawing employer must pay the plan its proportional share
    of the plan’s “unfunded vested benefits,” 
    29 U.S.C. § 1381
    (b)(1), which is “the difference between the present
    value of the plan’s vested benefits and the present value of its
    assets,” Connors v. B & H Trucking Co., 
    871 F.2d 132
    , 133
    (D.C. Cir. 1989); see 
    29 U.S.C. § 1393
    (c) (laying out this
    calculation).
    An actuary must make numerous assumptions to calculate
    an employer’s withdrawal liability. For example, to project the
    plan’s vested benefits, the actuary must make assumptions
    about how long employees will work and how long retirees will
    live. The actuary also must make an assumption about the
    discount rate, i.e., the rate at which the plan’s assets will earn
    5
    interest.3 The discount rate is the weightiest assumption in the
    overall withdrawal liability calculation. See Combs v. Classic
    Coal Corp., 
    931 F.2d 96
    , 101 (D.C. Cir. 1991) (explaining that
    an “erroneously low” discount rate, without appropriate
    offsetting assumptions, might “destroy the validity of the entire
    calculation” of unfunded vested benefits).
    In the absence of a relevant regulation, an actuary must
    calculate withdrawal liability using assumptions “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.” 
    29 U.S.C. § 1393
    (a)(1); see also
    
    id.
     § 1393(a)(2) (allowing the use of assumptions set forth in
    Pension Benefit Guaranty Corporation (“PBGC”) regulations).
    ERISA and the MPPAA lay out a system to adjudicate
    disputes over withdrawal liability. The pension plan is
    responsible for initially determining an employer’s withdrawal
    liability. Id. § 1382(1). If an employer wants to contest the
    plan’s determination, it must first do so through arbitration. Id.
    § 1401(a)(1). In those and all subsequent proceedings, a plan’s
    determination of unfunded vested benefits “is presumed correct
    unless a party contesting the determination shows by a
    preponderance of the evidence that” either “(i) the actuarial
    assumptions and methods used in the determination were, in
    3
    Because of the time value of money, a plan does not need to have
    $100,000 on hand in order to pay $100,000 in the future. The money
    the plan has on hand will be invested and earn interest; how much
    interest the assets will earn determines how much the plan must have
    on hand at the time the employer withdraws. The discount rate is the
    amount of interest the actuary assumes the plan’s assets will earn,
    which is used to convert the stream of future payments to employees
    into the present-day amount of assets needed to make those
    payments.
    6
    the aggregate, unreasonable (taking into account the experience
    of the plan and reasonable expectations), or (ii) the plan’s
    actuary made a significant error in applying the actuarial
    assumptions or methods.” Id. § 1401(a)(3)(B). After
    arbitration, any party can seek “to enforce, vacate, or modify
    the arbitrator’s award” in district court. Id. § 1401(b)(2). The
    court must apply a “presumption, rebuttable only by a clear
    preponderance of the evidence, that the findings of fact made
    by the arbitrator were correct.” Id. § 1401(c).
    B.
    The United Mine Workers of America 1974 Pension Plan
    is a multiemployer pension plan. Energy West was a
    participating employer in the Pension Plan but withdrew after
    closing its Utah mine in 2015. At the time of Energy West’s
    withdrawal, the Pension Plan was projected to become
    insolvent as early as 2022. Needless to say, the Pension Plan
    had a lot of unfunded vested benefits, requiring Energy West
    to pay withdrawal liability.4
    The job of calculating Energy West’s withdrawal liability
    fell to William Ruschau, the Pension Plan’s actuary. Ruschau
    testified that he used the Pension Plan’s prior experience as a
    guidepost for most of his assumptions but that he did not
    consider the Pension Plan’s historic investment performance to
    inform his discount rate assumption. Instead he “use[d] a
    reasonable risk-free interest rate,” which is equivalent to
    assuming the plan would “buy[] an annuity to settle up the
    4
    The Pension Plan’s financial problems were mitigated greatly by
    the Bipartisan American Miners Act of 2019, but that infusion of
    money “shall be disregarded … for purposes of determining [an]
    employer’s withdrawal liability.” Pub. L. No. 116-94, div. M,
    § 102(a)(3), 
    133 Stat. 2534
    , 3092 (codified at 
    30 U.S.C. § 1232
    (i)(4)(E)).
    7
    employer’s share of the unfunded vested benefits.” His
    justification for using risk-free rates was that when an
    employer withdraws from a plan, it no longer bears any risk
    associated with that plan’s investment performance.
    The choice of a risk-free rate made a material difference.
    If Ruschau had used a discount rate assumption based on the
    Pension Plan’s historic investment performance—around
    7.5%—Energy West’s withdrawal liability would have been
    about $40 million. United Mine Workers of Am. 1974 Pension
    Plan v. Energy W. Mining Co., 
    464 F. Supp. 3d 104
    , 111
    (D.D.C. 2020). Instead, Ruschau used a discount rate
    assumption of 2.71% for 2015 to 2035 and 2.78% for all years
    thereafter, based on the rates the PBGC projected risk-free
    annuities will earn. See 
    id.
     Applying that discount rate, Energy
    West’s withdrawal liability was over $115 million. See 
    id. at 120
    .
    Energy West disagreed with the discount rate assumption
    and pursued arbitration.5 It contended that the risk-free PBGC
    rate was an inappropriate choice for the discount rate
    assumption because (1) the actuary was required to “use the
    same or very similar rate for both withdrawal liability and
    [minimum] funding purposes,” and (2) risk-free rates are not
    the “best estimate of anticipated experience under the plan”
    because they are not based on past or projected investment
    performance.
    The arbitrator rejected both arguments. He agreed with the
    Pension Plan that using risk-free rates to calculate withdrawal
    5
    Energy West also contended that ERISA’s 20-year cap on
    withdrawal liability payments applied to it, but does not appeal the
    decisions of the arbitrator and the district court holding otherwise.
    See 
    id.
     at 120–25.
    8
    liability was reasonable, even though they were not used to
    calculate minimum funding, because withdrawal liability,
    unlike minimum funding, acts “as a settlement of the
    employer’s obligations.” In reaching this conclusion, the
    arbitrator placed great weight on Actuarial Standard of Practice
    27, Section 3.9(b), which states that “[a]n actuary measuring a
    plan’s present value of benefits on a … settlement basis may
    use a discount rate implicit in annuity prices or
    other … settlement options.” ACTUARIAL STANDARDS BOARD,
    ACTUARIAL STANDARD OF PRACTICE NO. 27: SELECTION OF
    ECONOMIC ASSUMPTIONS FOR MEASURING PENSION
    OBLIGATIONS § 3.9(b) (2013) (“ASOP 27”). The arbitrator read
    this section as approving the use of risk-free rates to calculate
    withdrawal liability on the theory that an employer’s
    withdrawal constitutes a settlement. He concluded that “almost
    by definition an actuary who applies the guidance of the
    actuarial standards of practice is using a combination of
    methods and assumptions that would be acceptable to a
    reasonable actuary.”
    Before the district court, Energy West sought to vacate,
    and the Pension Plan sought to enforce, the arbitration award.
    The court granted summary judgment to the Pension Plan and
    entered an order enforcing the arbitration award. See United
    Mine Workers of Am. 1974 Pension Plan, 464 F. Supp. 3d at
    125. The court rejected Energy West’s contention that the
    discount rate assumptions for minimum funding obligations
    and withdrawal liability had to be identical under the MPPAA.
    Pointing to the statute’s different language in the minimum
    funding section—requiring that “each” assumption be
    reasonable—and the withdrawal liability section—requiring
    that the assumptions be reasonable “in the aggregate”—the
    court held that different assumptions were permissible under
    the statute. See id. at 112–15. The court also rejected Energy
    West’s contention that the use of risk-free rates was
    9
    unreasonable because it was not the “best estimate of
    anticipated experience under the plan.” The court held that
    language meant only that the actuary must independently
    calculate withdrawal liability and that it did not impose any
    substantive requirements on the assumptions. Id. at 116–20.
    Energy West appealed.
    II.
    We review the district court’s grant of summary judgment
    de novo, which means, in essence, we are reviewing the
    arbitrator’s decision. Combs, 
    931 F.2d at 99
    . The arbitrator’s
    findings of fact are presumed correct unless they are rebutted
    “by a clear preponderance of the evidence,” 
    29 U.S.C. § 1401
    (c), and the arbitrator’s legal determinations are
    reviewed de novo, see I.A.M. Nat’l Pension Fund Benefit Plan
    C v. Stockton TRI Indus., 
    727 F.2d 1204
    , 1207 n.7 (D.C. Cir.
    1984).
    A.
    When calculating withdrawal liability, the MPPAA
    mandates that actuaries use “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.” 
    29 U.S.C. § 1393
    (a)(1). Energy
    West concedes that the “Aggregate Reasonableness
    Requirement” generally leaves the actuary with discretion to
    use his professional judgment about what assumptions are used
    to calculate withdrawal liability. The dispute here centers on
    whether the “Best Estimate Requirement” fetters that
    discretion. Energy West maintains that the Best Estimate
    Requirement mandates using assumptions based on the plan’s
    particular characteristics. The Pension Plan, on the other hand,
    asserts that the Best Estimate Requirement requires that the
    10
    assumptions be developed independently by the actuary but
    otherwise imposes no substantive requirements on the
    assumptions made.
    Energy West is correct that the actuary must make
    assumptions based on the plan’s particular characteristics when
    calculating withdrawal liability. This follows directly from the
    words of the statute. The MPPAA specifies that the
    assumptions must be “the actuary’s best estimate of anticipated
    experience under the plan.” 
    Id.
     (emphasis added). Congress
    directed what the actuary must estimate when making
    assumptions used to calculate withdrawal liability, namely a
    plan’s anticipated future liabilities and asset returns. Such
    predictions necessarily turn on a plan’s characteristics.
    The district court interpreted the Best Estimate
    Requirement to require only that the assumptions be made by
    the actuary; however, such an interpretation disregards the
    requirement that the actuary estimate the “anticipated
    experience under the plan.” 
    Id.
     “It is our duty to give effect, if
    possible, to every clause and word of a statute.” Duncan v.
    Walker, 
    533 U.S. 167
    , 174 (2001) (cleaned up). To give effect
    to every word of the Best Estimate Requirement, we interpret
    it to lay down both a procedural rule that the assumptions be
    made by the actuary and a substantive rule that the assumptions
    reflect the characteristics of the plan.
    As applied to the discount rate assumption, using the
    plan’s particular characteristics means the actuary must
    estimate how much interest the plan’s assets will earn based on
    their anticipated rate of return. An actuary cannot base the
    discount rate “on investments that the plan is not required to
    and might never buy, based on a set formula that is not tailored
    to the unique characteristics of the plan.” Sofco Erectors, Inc.
    v. Trustees of Ohio Operating Eng’rs Pension Fund, 
    15 F.4th 11
    407, 421 (6th Cir. 2021) (cleaned up). Thus, risk-free rates
    might be appropriate if a plan were invested in risk-free assets,
    or perhaps if it planned to invest the withdrawal liability
    payments in risk-free assets. But if the plan is currently and
    projects to be invested in riskier assets, the discount rate used
    to calculate withdrawal liability must reflect that fact.
    This interpretation of the Best Estimate Requirement is
    reinforced by comparison to other sections of ERISA.
    Congress has tailored the calculation of liabilities, providing
    distinct actuarial specifications for different circumstances. For
    example, benefits must be paid “in the form of an annuity”
    upon the “[t]ermination of a multiemployer plan,” which can
    occur when every employer withdraws from the plan. 29
    U.S.C. § 1341a(a)(2), (c)(2). When a plan terminates, PBGC
    regulations require that actuaries use a proxy for risk-free rates
    to value employees’ benefits. See 
    29 C.F.R. § 4281.13
    (a)
    (instructing actuaries to use the “interest assumptions” in the
    rate table for annuities). Similarly, ERISA directs actuaries to
    calculate minimum funding requirements “without taking into
    account the experience of the plan” when determining whether
    a plan has hit its full-funding limitation. 
    29 U.S.C. § 1084
    (c)(6)(E)(iii)(I). Such meaningful variation only bolsters
    the requirement to read the statute to mean what it says. When
    calculating withdrawal liability, actuaries must select a
    discount rate based on the plan’s actual anticipated investment
    experience. Accord Sofco Erectors, 15 F.4th at 422.
    Although the discount rate is only one of the assumptions
    used “in combination,” 
    29 U.S.C. § 1393
    (a)(1), to calculate the
    withdrawal liability, it is the most impactful, see Combs, 
    931 F.2d at 101
    . Therefore, if the actuary selects a discount rate that
    is not the “best estimate of anticipated experience under the
    12
    plan,” this error will usually render the calculation contrary to
    the MPPAA.
    We find unpersuasive the Pension Plan’s argument that the
    Best Estimate Requirement does not impose any substantive
    requirements on the assumptions but instead requires only that
    the assumptions come from the actuary. The Pension Plan
    relies on a series of out-of-circuit cases interpreting the Internal
    Revenue Code’s then-identical Best Estimate Requirement.6
    But the cases the Pension Plan cites involved a distinct question
    about whether the Best Estimate Requirement meant that the
    actuary had to choose a single “best” estimate, or rather could
    choose within a “reasonable” range of estimates. Other circuits
    have concluded that the actuary may choose within a
    reasonable range, because if the Best Estimate Requirement
    meant an actuary had to pick the single point assumption that
    he thought was “the most likely result,” then the requirement
    that the assumptions be “reasonable” would be “superfluous.”
    Vinson & Elkins v. Comm’r, 
    7 F.3d 1235
    , 1238 (5th Cir. 1993);
    see also Wachtell, Lipton, Rosen & Katz v. Comm’r, 
    26 F.3d 291
    , 296 (2d Cir. 1994) (explaining the statute “is not violated
    when an actuary chooses an assumption that is within the range
    of reasonable assumptions, even when the assumption is at the
    conservative end of that range”); Citrus Valley Ests., Inc. v.
    Comm’r, 
    49 F.3d 1410
    , 1415 (9th Cir. 1995) (same); Rhoades,
    6
    
    26 U.S.C. § 412
    (c)(3) (1994) (“For purposes of this section, all
    costs, liabilities, rates of interest, and other factors under the plan
    shall be determined on the basis of actuarial assumptions and
    methods … which, in the aggregate, are reasonable (taking into
    account the experiences of the plan and reasonable expectations),
    and … which, in combination, offer the actuary’s best estimate of
    anticipated experience under the plan.”).
    13
    McKee & Boer v. United States, 
    43 F.3d 1071
    , 1075 (6th Cir.
    1995) (same).
    The Pension Plan relies on the fact that, in reaching this
    holding, these circuits concluded the Best Estimate
    Requirement is “procedural,” meaning that the estimate must
    be the actuary’s alone. See Citrus Valley, 
    49 F.3d at 1414
    ;
    Rhoades, 
    43 F.3d at 1075
    ; Wachtell, 
    26 F.3d at 296
    ; Vinson &
    Elkins, 
    7 F.3d at 1238
    . But these cases generally did not hold
    that the Best Estimate Requirement was only procedural. See
    Wachtell, 
    26 F.3d at 296
     (“[T]he ‘best estimate’
    requirement … is principally designed to [e]nsure that the
    chosen assumptions actually represent the actuary’s own
    judgment rather than the dictates of plan administrators or
    sponsors.”) (emphasis added); Citrus Valley, 
    49 F.3d at 1414
    (quoting Wachtell); Rhoades, 
    43 F.3d at 1075
     (same).
    Rather, these cases analyzed only the first half of the Best
    Estimate Requirement—that the assumption be “the actuary’s
    best estimate.” As to the requirement that the assumptions be
    the “best estimate of anticipated experience under the plan,”
    these courts were either silent, see Vinson & Elkins, 
    7 F.3d at
    1237–39, or explicitly clarified that they were not reading it out
    of the statute, see Wachtell, 
    26 F.3d at 296
     (the statute “is not
    violated when an actuary chooses an assumption that is within
    the range of reasonable assumptions, even when the
    assumption is at the conservative end of that range, provided
    the chosen assumption is the actuary’s best estimate of
    anticipated plan experience.”) (emphasis added); Rhoades, 
    43 F.3d at 1075
     (quoting Wachtell).
    Nothing in these cases forecloses requiring the actuary to
    use the plan’s particular characteristics, which simply follows
    from the statutory requirement to determine the “best estimate
    of anticipated experience under the plan.” Therefore, these
    14
    cases do not support the Pension Plan’s argument that the Best
    Estimate Requirement does not mean what it says. Accord
    Sofco Erectors, 15 F.4th at 422 (holding that Rhoades, 
    43 F.3d at
    1073–75, does not “suggest[] that actuaries may disregard
    the statute’s requirement that they base their estimates on the
    ‘anticipated experience under the plan’”) (quoting 
    29 U.S.C. § 1393
    (a)(1)).
    In sum, the MPPAA’s rule that the actuary use
    assumptions “which, in combination, offer the actuary’s best
    estimate of anticipated experience under the plan” requires the
    actuary to choose a discount rate assumption based on the
    plan’s actual investments. 
    29 U.S.C. § 1393
    (a)(1). While there
    may be a reasonable range of estimates, the discount rate
    assumption cannot be divorced from the plan’s anticipated
    investment returns.
    The arbitrator found, and all agree, that the Pension Plan’s
    actuary chose the risk-free PBGC rates based on the theory that
    risk-free rates are appropriate for withdrawal liability because
    the withdrawn employer no longer bears risk. The discount rate
    assumption was not chosen based on the Pension Plan’s past or
    projected investment returns. Therefore, the PBGC rate
    assumption was not the actuary’s “best estimate of anticipated
    experience under the plan.”
    B.
    The Pension Plan gives two reasons why the arbitration
    award should not be vacated even if Energy West’s
    interpretation of the Best Estimate Requirement is correct.
    First, the Pension Plan asserts that using risk-free rates to
    calculate withdrawal liability is proper under ASOP 27,7 and
    7
    Specifically, the Pension Plan points to Section 3.9(b), which says
    to “use a discount rate implicit in annuity prices” when “measuring
    15
    that “[t]he Best Estimate Requirement does not override
    actuarial standards of practice.” But the MPPAA, not ASOP
    27, is the law. We also note that the standard actuarial practices
    recognize that legal requirements supersede any professional
    norms. See ASOP 27 § 1.2 (“If a conflict exists between this
    standard and applicable law (statutes, regulations, and other
    legally binding authority), the actuary should comply with
    applicable law.”). In other words, an unlawful assumption
    violates professional norms and is therefore “unreasonable.”8
    Whatever the merits of the actuary’s theory, it cannot displace
    the Best Estimate Requirement.9
    Second, the Pension Plan asserts that a violation of the
    Best Estimate Requirement is not a valid ground for vacating
    an arbitration award under the dispute resolution provision of
    the MPPAA. The statute specifies that “[i]n the case of the
    determination of a plan’s unfunded vested benefits for a plan
    year, the determination is presumed correct unless a party
    contesting the determination shows by a preponderance of
    evidence that ... the actuarial assumptions and methods used in
    the determination were, in the aggregate, unreasonable (taking
    a plan’s present value of benefits on a defeasance or settlement
    basis.” We express no opinion on the Pension Plan’s argument that
    withdrawal liability is an occasion where benefits are properly
    measured on a “defeasance or settlement basis.”
    8
    This remains true regardless of how widespread the unlawful
    practice is among the profession. Cf. The T.J. Hooper, 
    60 F.2d 737
    ,
    740 (2d Cir. 1932) (L. Hand., J.) (“[I]n most cases reasonable
    prudence is in fact common prudence; but strictly it is never its
    measure[.]”).
    9
    Under the MPPAA, the only alternative to the Best Estimate
    Requirement for calculating withdrawal liability is a PBGC
    regulation prescribing actuarial assumptions and methods. 
    29 U.S.C. § 1393
    (a)(2). But there is no relevant regulation here.
    16
    into account the experience of the plan and reasonable
    expectations).” 
    29 U.S.C. § 1401
    (a)(3)(B). The Pension Plan
    contends that because the dispute resolution provision does not
    specify that the presumption of correctness can be overcome
    by showing that the assumptions were not the “best estimate of
    anticipated experience under the plan,” such a showing cannot
    be grounds to vacate the arbitration.
    We disagree. The dispute resolution provision permits
    vacating an arbitration award if the actuarial assumptions were
    unreasonable in the aggregate “taking into account the
    experience of the plan.” 
    Id.
     § 1401(a)(3)(B)(i). The Aggregate
    Reasonableness Requirement, both for dispute resolution and
    for withdrawal liability in Section 1393(a)(1), does not just
    require assumptions that are reasonable in the abstract; it
    requires assumptions that are reasonable relative to the plan,
    taking the plan’s experience into account. If the actuary is not
    basing the assumptions on the plan’s characteristics, the
    assumptions will not be reasonable “taking into account the
    experience of the plan.” In other words, not only must the
    actuary’s assumptions be reasonable, they must be aimed at the
    right calculation, namely the predicted future of the plan.
    Here the discount rate assumption used to calculate
    unfunded vested benefits did not take into account the
    experience of the plan and therefore was not a reasonable
    assumption. Thus, Energy West raised a valid ground for
    vacating the arbitration award.
    ***
    The arbitration award must be vacated because in
    determining the withdrawal liability for Energy West, the
    actuary failed to use a discount rate that reflected the Plan’s
    17
    characteristics and was the “best estimate of anticipated
    experience under the plan.”
    III.
    Having decided that the arbitration award must be vacated,
    we nonetheless address Energy West’s argument that the
    discount rate assumption used for withdrawal liability and
    minimum funding must be the same because a resolution of this
    question is relevant to the scope of acceptable calculations of
    Energy West’s withdrawal liability. We hold that the
    assumptions need not be identical but must be similar because
    they both must be “the actuary’s best estimate of anticipated
    experience under the plan.”
    The current provisions governing the assumptions for
    minimum funding and withdrawal liability are similar, but not
    identical. When the MPPAA was enacted, an identical rule
    applied to actuarial assumptions used to calculate a plan’s
    minimum funding obligations and an employer’s withdrawal
    liability. Compare 
    29 U.S.C. § 1082
    (c)(3) (1982), with 
    id.
    § 1393(a)(1). In the Pension Protection Act of 2006, Congress
    tweaked the rule for calculating minimum funding obligations,
    but left the language regarding withdrawal liability
    assumptions unchanged. See Pub. L. No. 109-280, § 201, 
    120 Stat. 780
    , 862 (codified at 
    29 U.S.C. § 1084
    (c)(3)). This means
    that for withdrawal liability, actuaries must use “actuarial
    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.” 
    29 U.S.C. § 1393
    (a)(1). For minimum funding, on the
    other hand, actuaries must use “actuarial assumptions and
    methods—(A) each of which is reasonable (taking into account
    the experience of the plan and reasonable expectations), and
    18
    (B) which, in combination, offer the actuary’s best estimate of
    anticipated experience under the plan.” 
    Id.
     § 1084(c)(3).
    Both provisions require using assumptions that reflect “the
    actuary’s best estimate of anticipated experience under the
    plan.” For the reasons given above, this Best Estimate
    Requirement means that, for both calculations, the assumptions
    must be based on the actual characteristics of the plan. The
    discount rate specifically must reflect the interest the plan’s
    assets are projected to earn. Because the discount rate
    assumptions for calculating withdrawal liability and minimum
    funding must be estimates of the same thing, they will
    invariably be similar. It is difficult, for example, to imagine
    they could diverge by nearly five hundred basis points, as they
    did here.
    But it does not follow that the discount rates must be
    identical. The Best Estimate Requirement does not mandate
    adopting any single numerical assumption. As other circuits
    have held, there is an “acceptable range.” Citrus Valley, 
    49 F.3d at 1415
    . And that must be so because if the Best Estimate
    Requirement forced actuaries to use the single most accurate
    estimation for each assumption, the requirement that the
    assumptions be reasonable would be “superfluous.” Vinson &
    Elkins, 
    7 F.3d at 1238
    . Nothing in the statutory text indicates
    the assumptions for minimum funding and withdrawal liability
    must fall at the same point in the acceptable range of estimates
    based on the plan’s characteristics. The assumed discount rates
    must be similar, even if not always the same.
    This conclusion is supported by the somewhat different
    statutory language governing the assumptions for minimum
    funding and withdrawal liability. For withdrawal liability,
    actuaries must use assumptions “which, in the aggregate, are
    reasonable.” 
    29 U.S.C. § 1393
    (a)(1). Because the assumptions
    19
    must be reasonable “in the aggregate,” it may be possible for
    one unreasonable assumption to offset another, leading to an
    overall reasonable withdrawal liability calculation. Combs, 
    931 F.2d at 101
    .10 For minimum funding, on the other hand,
    actuaries must use assumptions “each of which is reasonable.”
    
    29 U.S.C. § 1084
    (c)(3). Since “each” assumption must be
    reasonable, there is no possibility of offsetting assumptions for
    minimum funding calculations. Thus, the different statutory
    requirements suggest the possibility at least that different
    assumptions could be used for each calculation, so long as both
    assumptions are based on the plan’s actual characteristics.
    Energy West maintains that the Supreme Court held the
    assumptions used to calculate minimum funding and
    withdrawal liability must be identical in Concrete Pipe, 
    508 U.S. at
    615–36. Concrete Pipe, however, did not so hold. In
    considering the constitutionality of a provision of the MPPAA,
    the Court explained that “[t]he statutory requirement (of
    actuarial assumptions and methods—which, in the aggregate,
    are reasonable) is not unique to the withdrawal liability context,
    for the statute employs identical language in” the minimum
    funding context. 
    Id. at 632
     (cleaned up). When Concrete Pipe
    was decided, the provisions for minimum funding and
    withdrawal liability were still identical. Compare 
    29 U.S.C. § 1082
    (c)(3) (1988), with 
    id.
     § 1393(a)(1). As the Court
    explained, that identical language “tends to check the actuary’s
    discretion” because “[u]sing different assumptions for different
    purposes could very well be attacked as presumptively
    10
    Nothing in the record suggests, nor does any party contend, that
    there were offsetting assumptions in this case.
    20
    unreasonable both in arbitration and on judicial review.”
    Concrete Pipe, 
    508 U.S. at 633
     (cleaned up).
    The Court’s reasoning suggests that actuaries must
    typically use the same discount rate assumption. But the Court
    stopped short of holding that the statute required actuaries to
    use identical rates, even when the statutory provisions for
    withdrawal liability and minimum funding were identical. To
    hold that using different assumptions “could very well be
    attacked as presumptively unreasonable” is not to hold that that
    the assumptions must be the same as a matter of law. 
    Id.
    (cleaned up); see N.Y. Times Co. v. Newspaper & Mail
    Deliverers’—Publishers’ Pension Fund, 
    303 F. Supp. 3d 236
    ,
    254 (S.D.N.Y. 2018). Moreover, even if Concrete Pipe had
    held the assumptions must be identical, after the 2006
    amendment to the minimum funding provision that holding
    may no longer be good law. See Manhattan Ford Lincoln, Inc.
    v. UAW Local 259 Pension Fund, 
    331 F. Supp. 3d 365
    , 389–90
    (D.N.J. 2018).
    Our holding that the discount rates used to calculate
    minimum funding and withdrawal liability must be similar
    accords perfectly with Concrete Pipe, because both rates must
    be the actuary’s “best estimate of anticipated experience under
    the plan.”
    ***
    To calculate Energy West’s withdrawal liability from the
    Pension Plan, the actuary was required to base his assumptions
    on the Plan’s actual characteristics. Because the actuary failed
    to do so, we reverse the judgment of the district court and
    remand for vacatur of the arbitration award. When the actuary
    calculates Energy West’s withdrawal liability, the discount rate
    21
    assumption must be similar, but need not be identical, to the
    discount rate assumption used to calculate minimum funding.
    So ordered.