Kenneth Griffin's bad year just got a lot worse, making it even more difficult for him to collect the big fees that made him one of the country's richest fund managers.

Mr. Griffin's Citadel Investment Group in Chicago lost about 13% in November, bringing its investment decline to 47% during 2008, according to investors. Tabulating those losses and client withdrawals, the firm's total assets are expected to fall to $12 billion at year end from a peak near $20 billion in January, when the firm was planning an initial public...