The $107-billion California Public Employees' Retirement System will revamp the way it manages its $4.2-billion real estate portfolio in a move to boost returns. The nation's largest public pension fund will seek bids from managers who specialize in one of the four property types--apartments, retail, industrial and office--that make up its "core" real estate portfolio. They'll ask these managers to dedicate a team of investors to work exclusively for them and to consider investing their own money along with the fund's. They'll pay the managers based on their returns. CalPERS' real estate returns have been disappointing.