This is another ploy to entice sellers. The market maker runs the stock up with a tight spread in a fast market. Then he cools the buying interest by opening or widening the spread. After the buying has dropped, he lowers the offer below the last trade for a small trade. Next he tightens the spread so as to make weak sellers feel they can make a quick profit by selling to him at the bid on the tightened spread. Once the selling begins, the market maker “walks it down” by making small trades on the way down, all the while with tight spreads