(1) The reserve for investment income is created. The state treasurer shall credit to the reserve for investment income all interest, dividends, and other income from the investment of retirement system assets except for those of the reserve for health benefits created under section 214. The retirement system shall credit to the reserve for investment income all gifts and bequests to the retirement system; all forfeited contributions received pursuant to section 210; a surplus in any reserve created by this act except for those of the reserve for health benefits created under section 214; and all other money for which there is no specific disposition provided.

    (2) Except as otherwise provided in this subsection, the retirement system shall annually credit interest on the preceding year balances in the reserve for member contributions, reserve for employer contributions, and the reserve for retirement benefits. However, the retirement system shall begin to calculate interest on member contributions made within a calendar year on the first day of the calendar year following the contribution and shall credit the interest on member contributions at the end of the calendar year. The retirement system shall charge the reserve for investment income the interest credited to the reserves under this subsection.

    (3) The retirement system shall pay the expenses for the administration of the retirement system, exclusive of amounts payable as retirement allowances and other benefits provided in this act, from the reserve for investment income.