When a yield curve accounting interest rate assumption is used in a Valuation Set or a forecast, a single equivalent effective discount rate is calculated and used in the exhibit developing accounting expense. In U.S. Qualified, universal, and Canadian modes, the effective discount rate is calculated on either a PBO or PBO Annuity substitution basis. In all other modes, it is calculated on a PBO or APBO basis (OPEB mode). It is the single equivalent interest rate that, if used as a constant interest rate assumption, would produce the same PBO or APBO as the specified yield curve.  For most accounting methodologies, this rate is used to bring forward the service cost to the end of the year and (together with any additional amount added to the rate, as specified by the Interest Cost rate equals Discount Rate plus parameter of the Accounting Methodology topic of the Asset & Funding Policy) to calculate the interest cost.

It is important to note that all valuation results, as well as core projections and their corresponding interpolated forecast results are calculated using the full yield curve. Thus the service cost, for example, will not be reproducible using the effective discount rate, because its duration, and therefore its single equivalent rate, differs from the PBO / APBO-based rate that ProVal uses.