attributable liability
(3) For purposes of this section, the term— (A) “attributable liability” means the excess, if any, determined under the provisions of a plan not inconsistent with regulations of the corporation, of— (i) the value of vested benefits accrued as a result of service with the employer, over (ii) the value of plan assets attributed to the employer, and (B) “unattributable liability” means the excess of withdrawal liability over attributable liability. Such terms may be further defined, and the manner in which they shall be applied may be prescribed, by the corporation by regulation.