29 C.F.R. § 4022.51

(a) Amount of unfunded nonguaranteed benefits. For purposes of this section, and subject to paragraph (b) of this section, a plan's amount of unfunded nonguaranteed benefits means the plan's outstanding amount of benefit liabilities, as defined in section 4001(a)(19) of ERISA, determined as of the plan's termination date. A plan's amount of unfunded nonguaranteed benefits is multiplied by the applicable recovery ratio to determine the aggregate amount to be allocated with respect to participants of the plan under section 4022(c)(1) of ERISA.

(b) Benefits included in unfunded nonguaranteed benefits. For purposes of computing benefits under section 4022(c) of ERISA in a PPA 2006 bankruptcy termination, unfunded nonguaranteed benefits are benefits under a plan as of the plan's termination date that are neither guaranteed by PBGC (taking into account section 4022(g) of ERISA) nor funded by the plan's assets (taking into account section 4044(e) of ERISA).

(c) Determination of recovery ratio. In a PPA 2006 bankruptcy termination, the recovery ratio under section 4022(c)(3) of ERISA is determined as follows. The numerator is based on PBGC's recoveries under section 4062, 4063, or 4064, valued as of the plan's (or plans') termination date (or dates). The denominator of the recovery ratio is based on the amount of unfunded benefit liabilities, as defined in section 4001(a)(18) of ERISA, as of the plan's (or plans') termination date (or dates).