Examples of Suspicious Pricing Action, page-274

I remember reading years ago that the major trading companies pay the exchanges to have their black boxes plugged directly into the exchanges. It gives them nano-second advantages over everyone else, and the algorithms allow them to front-run the market, whether moving up or down. Of course the exchange says it is "legal", because they are party to the arrangement. As for the tiny trades which can manipulate the market, much the same applies, and of course they do not pay the same fees as Joe Public.