Effective with calendar years ending after January 1, 2000, the board shall make contributions to defined contribution accounts established on behalf of members of the retirement system. In addition, members of the retirement system who are not members of LAGERS shall contribute to this defined contribution program. The board’s contributions shall be made from the revenues described in subsections 1 and 3 of section 50.1020, and sections 50.1190 and 50.1200, but only if it is determined that the entire amount of such revenues need not be contributed to the retirement system described in sections 50.1000 to 50.1200 in order to keep such retirement system actuarially sound. The provisions of sections 50.1220 to 50.1260 shall apply exclusively to the program described in this section.