(a) When periodic retirement or survivors' benefits are payable under 42 U.S.C. 401 - 433 (Title II, Social Security Act), the weekly compensation provided for in this chapter shall be reduced by an amount equal as nearly as practicable to one-half of the federal periodic benefits for a given week.

(b) When it is determined that, in accordance with 42 U.S.C. 401 - 433, periodic disability benefits are payable to an employee or the employee's dependents for an injury for which a claim has been filed under this chapter, weekly disability benefits payable under this chapter shall be offset by an amount by which the sum of (1) weekly benefits to which the employee is entitled under 42 U.S.C. 401 - 433, and (2) weekly disability benefits to which the employee would otherwise be entitled under this chapter, exceeds 80 percent of the employee's average weekly wages at the time of injury.

(c) If employer contributions to a qualified pension or profit sharing plan have been included in the determination of gross earnings and the employee is receiving pension or profit sharing payments, weekly compensation benefits payable under this chapter shall be reduced by the amount paid or payable to the injured worker under the plan for any week or weeks during which compensation benefits are also payable. The amount of the reduction may not in any week exceed the increase in weekly compensation benefits brought about by the inclusion of employer contributions to a qualified pension or profit sharing plan in the determination of gross earnings.