The County Equal Retirement Benefit Fund is created. The fund shall be administered by the board. Each county participating in the retirement system on January 1, 1984, pursuant to the County Employees Retirement Act shall make a contribution at least once a year to the fund, in addition to any other retirement contributions. Such contribution shall be in an amount determined by the board to provide all similarly situated male and female members of the retirement system with equal benefits pursuant to subsection (2) of section 23-2317 and to provide for direct expenses incurred in administering the fund. The board shall keep a record of the contributions made by each county. Any money in the fund available for investment shall be invested by the state investment officer pursuant to the Nebraska Capital Expansion Act and the Nebraska State Funds Investment Act.