Comment on: "Two-phase behaviour of financial markets"

In a recent article [Nature 421, 130 (2003)], Plerou, Gopikrishnan and Stanley report some evidence for an intriguing two-phase behavior of financial markets when studying the distribution of volume imbalance conditional to the local intensity of its fluctuations. We show here that this apparent phase transition is a generic consequence of the conditioning and exists even in the absence of any non trivial collective phenomenon.