53 Pa. Stat. § 30557
The members of the board shall be trustees of the fund created by this act and shall have exclusive management of said fund, with full power to invest the moneys therein, subject to the terms, conditions, limitations and restrictions imposed by law upon fiduciaries. Subject to like terms, conditions, limitations and restrictions, said trustees shall have power to hold, purchase, sell, assign, transfer or dispose of any of the securities and investments in said funds, as well as the proceeds of said investments and of the moneys belonging to said fund.
The board shall annually allow regular interest on the mean amount for the preceding year to the credit of each of the accounts created in accordance with the provisions of this act. The amount so allowed shall be credited to each contributor's account.
53 P.S. § 30557