(1) As used in this act, "after-tax average weekly wage" means average weekly wage as defined in section 371 reduced by the prorated weekly amount which would have been paid under the federal insurance contributions act, 26 U.S.C. 3101 to 3126, state income tax and federal income tax, calculated on an annual basis using as the number of exemptions the disabled employee's dependents plus the employee, and without excess itemized deductions. Effective January 1, 1982, and each January 1 thereafter, the applicable federal and state laws in effect on the preceding July 1 shall be used in determining the after-tax weekly wage.

    (2) Each December 1 the director shall publish tables of the average weekly wage and 80% of after-tax average weekly wage that are to be in effect on the following January 1. These tables shall be conclusive for the purpose of converting an average weekly wage into 80% of after-tax average weekly wage.