(1)    This section shall be construed as an enactment of statewide concern to encourage career public service by employees of the state, 1st class cities and counties having a population of 750,000 or more but shall not be construed to affect the authority of any 1st class city to exercise its power granted under article XI, section 3, of the constitution and chapter 441, laws of 1947, section 31 over any other provisions of any of the retirement systems established by chapter 589, laws of 1921, chapter 423, laws of 1923 or chapter 396, laws of 1937, or to affect the authority of any county having a population of 750,000 or more to exercise its power granted under chapter 405, laws of 1965, over any other provisions of the retirement system established by chapter 201, laws of 1937.

   (2)   Except as provided in sub. (7), any individual who has vested annuity benefit rights under the Wisconsin retirement system or under one of the retirement systems established by chapter 589, laws of 1921, chapter 423, laws of 1923, chapter 201, laws of 1937 or chapter 396, laws of 1937, who subsequently becomes covered by one or more of those other retirement systems, who, on or after May 11, 1990, terminates all employment covered by any of those retirement systems and who applies to have benefits begin within a 60-day period under all of those retirement systems from which the individual is entitled to receive benefits may, on a form provided by and filed with the department, elect to have retirement benefit computations and eligibility under each of those retirement systems determined as provided in this section.

   (3)   The sum of all service credited to the individual under each retirement system specified in sub. (2) shall be used in determining whether the individual has met any vesting period required for retirement benefit eligibility during any subsequent employment covered by any retirement system specified in sub. (2), but shall not be used in determining the amount of the benefit nor in determining credit for military service.

   (4)   The individual’s retirement benefits under each retirement system specified in sub. (2) shall be determined as follows:

      (a)    The benefit formula used for each type of service credited to the individual shall be the benefit formula in effect for that type of service under the respective retirement system on the date on which the individual terminated all employment covered by any retirement system specified in sub. (2).

      (b)    Subject to federal annual compensation limits, the final average salary or final average earnings used in the benefit formula computation for each retirement system under par. (a) shall be the individual’s final average salary or final average earnings under the respective retirement system, determined in accordance with the provisions of that retirement system based on the earnings covered by that retirement system and on all service permitted under that retirement system to be used in determining the final average salary or final average earnings, increased by the percentage increase in the average of the total wages, as determined under 42 U.S. Code § 415 (b) (3) (A), between the date on which the individual terminated all employment covered by that retirement system and the date on which the individual terminated all employment covered by any of those retirement systems.

   (5)   The benefits computed under this section for each retirement system shall be in lieu of any other benefit payable by that retirement system and may not begin before the individual terminates all employment covered by any retirement system specified in sub. (2).

   (6)   The secretary may promulgate rules affecting any retirement system specified in sub. (2) to carry out the purposes of this section.

   (7)   

      (a)    Retirement benefit computations or eligibility may not be determined as provided in this section with respect to service performed by an individual under any retirement system established by chapter 589, laws of 1921, chapter 423, laws of 1923, or chapter 396, laws of 1937, or to service performed by that individual under the Wisconsin retirement system, before the date on which the governing body of the city that established the retirement system under chapter 589, laws of 1921, chapter 423, laws of 1923, or chapter 396, laws of 1937, adopts a resolution approving the application of this section to the retirement benefit computations and eligibility determinations under all of those retirement systems that it has established.

      (b)    Retirement benefit computations or eligibility may not be determined as provided in this section with respect to service performed by an individual under a retirement system established by chapter 201, laws of 1937, or to service performed by that individual under the Wisconsin retirement system, before the date on which the governing body of the county that established the retirement system under chapter 201, laws of 1937, adopts a resolution approving the application of this section to the retirement benefit computations and eligibility determinations under that retirement system.

      (c)    A resolution adopted under par. (a) or (b) is irrevocable. Any governing body that adopts a resolution under par. (a) or (b) shall provide the department with a copy of the resolution.