MD is the easiest mean to get flush out would be sellers especially in a "more" bullish market. If you follow the common saying - "go with the trend" until it changes - why would you see a whole stake of sellers?
Everyone would try to stay with the trend and not go for quick profit. The only possible rationale - day traders who have reached their target and want to be out. But even then - why would they show their hands? as they can only sell at a much lower price.
To be me - it is a pretty straight forward tactic to get people to sell out to people who realised that they have "missed" the opportunity to jump in and are now waiting for pullback to jump on board.
This is a volatile market but the post depression fear factors are pretty much gone. Growth would be slow or anemic at best but the deceleration has slowed down.
