Wis. Stat. § 646.21: Custody and investment of assets.

(1) Custody. Except as provided in sub. (2), the board controls the assets of the fund. The board shall select regulated financial institutions in this state which receive deposits in which to establish and maintain accounts for assets needed on a current basis. If practicable, the accounts shall earn interest.

(2) Investment of assets. The board may request that assets of the fund not needed currently be invested by the investment board under s. 25.17. If so requested, the investment board shall invest those assets in investments with maturities and liquidity appropriate to the probable needs of the fund for money to perform its duties. All income attributable to the investments shall be credited to the fund, and both income and principal shall be transferred to the fund on request of the board. Assets held by the fund shall be invested in a similar manner.