Could be the market makers Reading Market-Maker Signals See the signs and messages they send each other
Many traders believe that market makers will "signal" moves in advance buy using small amounts of buys or sells as "signals". The "signals" are from one market maker to another.
100 I need shares. 200 I need shares badly, but do not take the stock down. 300 Take (or I am taking) the price down so I can load shares 400 Keep trading it sideways. 500 Gap the stock.