(a) When reduction is effective. A reduction for other disability benefits begins with the first month the employee is receiving both a disability annuity and workers' compensation or a public disability benefit. The reduction ends with the month before the month in which the employee becomes 65 years old or with the month in which the workers compensation or public disability benefit ends.
(b) Amount of reduction. The reduction for other disability benefits equals the difference between—
(1) The total tier I rates of the employee, spouse, and divorced spouse, before any reductions (age, public pension, social security benefits, etc.) plus the monthly amount of the workers' compensation of public disability benefit; and
(2) The higher of—
(i) Eighty percent of the employee's average current earnings, as defined in this section; or
(ii) The total tier I rates, as described in paragraph (b)(1) of this section.
(c) Average current earnings, defined. An employee's “average current earnings” is the highest of—
(1) The average monthly wage (AMW) used to compute the tier I AMW PIA. (The earnings are not indexed, even if the tier I PIA which is being paid is based on average indexed monthly earnings. See part 225 of this chapter.); or
(2) One-sixtieth of the employee's total earnings covered under either the Social Security or Railroad Retirement Acts (including earnings that exceed the maximum earnings used in computing social security benefits) for the five consecutive years after 1950 in which the employee had the highest earnings. The result, if not a multiple of $1, is rounded to the next lower multiple of $1; or
(3) One-twelfth of the employee's total earnings covered under either the Social Security or Railroad Retirement Acts (including earnings that exceed the maximum earnings used in computing social security benefits) for the year of highest earnings in the period which includes the year in which the employee became disabled and the five preceding years. The result, if not a multiple of $1, is rounded to the next lower multiple of $1.