Since January, bitcoin trading volume on exchanges has been slowly dropping (more or less, on average), but it's had a significant drop around May 13th, and has stayed low since then. I checked the volume from BTC China mainly, but it seems several (if not all) exchanges exhibit this phenomenon. Up to this point, I'm just stating facts.
My question is: does anybody know about any reasonable explanation for this? I mean, based on facts, evidence, or meaningful experience on the subject. For example, has this happened before? If so, it could be some temporary/cyclic phenomenon, maybe (?). Also, if this happens to be some sort of pattern that has occurred before, can we expect the volume to go up again anytime soon? Is it some sort of "bad sign" ? (as in "this pattern is often followed by a big crash" or something like that).
I know nobody has the crystal ball, and I'm not asking for unfounded opinions; I just thought that maybe someone with more financial experience or knowledge on the subject (than me, which shouldn't be very hard) could shed some light on this.