Mich. Comp. Laws § 38.1009

Sec. 9. (1) "Salary" means the compensation, common to all legislators, exclusive of travel allowance, paid by the state for 1 year of service as a legislator. A member shall contribute to the retirement system based on the percentage applied to that salary. (2) For purposes of section 23, salary also includes an additional 2% through December 30, 1986, and 4% beginning December 31, 1986, compounded annually and added for each year or portion of a year that expires after the member terminates service and before the member retires, of the member's greatest salary determined pursuant to subsection (1) received in 1 calendar year. This subsection only applies to a member who first becomes a member on or before January 1, 1995, and whose service terminates on or after December 1, 1978. (3) For purposes of section 23, for a member who left service before December 1, 1978, salary also includes an additional 2% for each year beginning January 1, 1979 through December 30, 1986 and 4% beginning December 31, 1986, compounded annually and added for each year or portion of a year that expires after the member terminates service and before the member retires, of the member's greatest salary determined pursuant to subsection (1) received in 1 calendar year. (4) For purposes of section 23, salary also includes an amount equal to the greatest amount of additional compensation received in 1 calendar year as a result of being in a leadership position, divided by 5, and then multiplied by the number of years or portion of a year, not to exceed 8, in which the member was in a leadership position and received additional compensation. Before a member who first becomes a member on or before January 1, 1995, may have the additional compensation included in salary under this subsection, the member shall pay to the retirement system a sum equal to 9% of the total additional compensation received. Before a member who first becomes a member after January 1, 1995, may have the additional compensation included in salary under this subsection, the member shall pay to the retirement system a sum equal to 7% of the total additional compensation received.