(1)    In this section, “county” means any county having a population of 750,000 or more.

   (2)   

      (a)    Beginning on July 1, 2011, in any employee retirement system of a county, except as otherwise provided in a collective bargaining agreement entered into under subch. IV of ch. 111 and except as provided in pars. (b) and (c), employees shall pay half of all actuarially required normal cost contributions for funding benefits under the retirement system. The employer may not pay on behalf of an employee any of the employee’s share of the actuarially required contributions.

      (b)   

         1.    An employer shall pay, on behalf of a nonrepresented law enforcement or fire fighting managerial employee, who was initially employed by the employer before July 1, 2011, the same contributions required by par. (a) that are paid by the employer for represented law enforcement or fire fighting personnel who were initially employed by the employer before July 1, 2011.

         2.    An employer shall pay, on behalf of a represented law enforcement or fire fighting employee, who was initially employed by the employer before July 1, 2011, and who on or after July 1, 2011, became employed in a nonrepresented law enforcement or fire fighting managerial position with the employer, or a successor employer in the event of a combined department that is created on or after July 1, 2011, the same contributions required by par. (a) that are paid by the employer for represented law enforcement or fire fighting personnel who were initially employed by the employer before July 1, 2011.

      (c)    In any employee retirement system of a county that has elected to become a participating employer under the Wisconsin Retirement System under s. 40.21 (1), except as provided in par. (b), irrespective of the funding status of the retirement system, the employer shall pay the remaining balance of actuarially determined normal cost contributions each year that is not covered by the employee contributions.

   (3)   No individual who is receiving an annuity under an employee retirement system of a county and who is reemployed by the county may continue to receive the annuity if a similarly situated individual who is receiving an annuity under the Wisconsin Retirement System and who was reemployed by a participating employer under that system would be required to terminate the annuity.

   (4)   Amortization period for employer contributions. Notwithstanding any provision of law or actuarial rule, beginning on January 1, 2024, in any retirement system established under chapter 201, laws of 1937, the required annual employer contribution shall be calculated using not more than a 30-year amortization period and an annual investment return assumption that is the same as or less than the annual investment return assumption used by the Wisconsin Retirement System for participating employees, as defined in s. 40.02 (46). Future unfunded actuarial accrued liability due to factors such as market returns and standard actuarial practices may be amortized on the basis of standard actuarial practices. The amortization period and investment return assumptions in this subsection shall supersede any amortization period and investment return assumption adopted by the retirement system’s actuary or retirement board. No trustee or administrator of a retirement system of any retirement system established under chapter 201, laws of 1937, shall be subject to liability for complying with this subsection.