This method applies if the worker is eligible in 1979 or later, and this is a disability case with more than one period of disability, or if this is an old-age or survivor case with a prior period of disability.
The PIA at entitlement to the current benefit is equal to the PIA at cessation of the prior period of disability. In addition, if the cessation was within 12 months of the current entitlement, any intervening cost-of-living adjustments are applied to the prior PIA.
For a disability benefit, or any benefit prior to January 1996, the MFB is simply the one at the date of cessation of the prior disability benefit. For old-age or survivors in 1996 or later, if the prior MFB was based on the disability maximum, the PIA at cessation must be deconverted back to the year of eligibility (by dividing out any cost-of-living adjustments), then that is used to compute a raw MFB, and that is converted forward (by applying cost-of-living adjustments) to the cessation date.
For more information on the disability guarantee or the disability maximum, see the OASDI Digest.