'Portfolio trading is an art unlike any other,' says one broker. It is one of those desks that doesn't seem to fit neatly into an investment bank's structure.

Since portfolio trading chiefly involves cash equities, there is a case for integrating it with the equities desk. But since it uses sophisticated quantitative methods like those in equity derivatives trading, it may fit in better with that desk. Some institutions, concerned about confidentiality, elect to keep it entirely separate. For them, preventing information leakage into the market - or even an appearance of front-running - takes precedence over considerations of efficiency or liquidity .