The case asks whether the "as of" language in 29 U.S.C. § 1391 establishes a deadline for the selection of actuarial assumptions used to calculate withdrawal liability. Specifically, it addresses whether these assumptions must be selected on or before the measurement date, which is the last day of the plan year preceding the employer's withdrawal. The Court must determine if actuaries may instead select these assumptions after the measurement date.

• The "as of" language in 29 U.S.C. § 1391 requires that actuarial assumptions be "frozen" on the measurement date.
• Actuarial assumptions are factual inputs into the calculation of unfunded vested benefits, similar to hard data such as the number of plan beneficiaries.
• ERISA contains a broad antiretroactivity principle, as evidenced by 29 U.S.C. § 1394, which prohibits applying new "plan rule or amendment" to withdrawal liability if adopted after the employer withdraws.
• Allowing plans to adopt assumptions after the measurement date invites manipulation, enabling plans to retroactively select assumptions to increase an employer's liability.

• The "as of" requirement in 29 U.S.C. § 1391 applies to the hard data feeding the calculation, not the tools used to perform the calculation.
• Actuarial assumptions are predictive judgments and tools rather than observable facts that are "in effect" on a specific date.
• 29 U.S.C. § 1393 requires actuaries to provide their "best estimate," which may necessitate using the most up-to-date data available after the measurement date.
• There is no textual deadline for the selection of assumptions in 29 U.S.C. § 1393.

• The Court held that 29 U.S.C. §§ 1391 and 1393 do not require actuarial assumptions to be selected on or before the measurement date.
• Regarding 29 U.S.C. § 1391, the Court reasoned that "as of" is understood "to assign an event to one time and the recognition of it to another," citing W. Follett, *Modern American Usage*.
• The Court distinguished between "hard data" (factual inputs fixed on the measurement date) and actuarial assumptions, which are "predictive judgments" and tools used for calculation.
• The Court noted that 29 U.S.C. § 1393(a)(1) groups assumptions with "methods," and professional guidelines in Actuarial Standard of Practice No. 27 (ASOP No. 27) indicate assumptions are selected for specific measurements.
• The Court applied the principle from *Romag Fasteners, Inc. v. Fossil Group, Inc.* that it does not generally read limitations into statutes that do not appear in the text.
• Citing *Russello v. United States*, the Court presumed the omission of a deadline in § 1393 was intentional because Congress included a similar deadline in 29 U.S.C. § 1399(c)(1)(A)(ii).
• The Court reasoned that the requirement in 29 U.S.C. § 1393(a)(1) to offer the "best estimate" supports post-measurement selection to avoid relying on stale data.
• The Court rejected the application of 29 U.S.C. § 1394, finding that its antiretroactivity limits apply to "plan rule or amendment," not actuarial assumptions.
• The Court concluded that policy concerns regarding manipulation cannot "trump the best interpretation of the statutory text," citing *Patel v. Garland*.