The California Public Employees' Retirement System (Calpers), the largest pension fund in the world, hopes to announce its new chief executive within the next two months after incumbent James Burton said he would leave earlier than expected.

Burton will leave Calpers on August 23 to become chief executive of the World Gold Council. In May, Burton, who has headed up Calpers for nearly eight years, announced his resignation, saying that he would remain at the fund until the autumn.