As you undoubtedly know, the actuary must follow the Labor Code section 1393(a) in setting the discount assumption for withdrawal liability. The law that the actuary must follow in setting the discount rate for funding purposes has similar -- but not identical -- language in section 1084(c).
You probably also know that the employer has a larger burden to overcome regarding the appropriateness of actuarial assumptions used for withdrawal liability. Regardless, you probably want to start by reviewing the stated reasons by the actuary as to why he/she thinks one discount rate is reasonable for funding and a different rate is reasonable for withdrawal liability.
