It was an old stock broker who'd explained to me how the MM's would use market orders to drop, or raise the share price in the manner that occurred today. A market order assures execution, but you may buy at a much higher price than the current ask, or sell well below the current bid price as the MM's play their games. I don't think things have changed over the many years that my broker explained it to me.
Of course today computers have much more to do with trading, but I still believe that market orders are where the MM's have the greatest opportunity to play games.
Gary
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