Here's an article by some pros... On NYSE "trade throughs" and "out of sequence prints". It may be 4 years old... but I doubt much has changed. http://www.hedgefundnews.com/news_n_info/article_detail.php?id=266 Their Conclusions: (1) You are entirely at the mercy of an NYSE that is above the law... Because the "out of sequence print" is a license to steal. (2) Honest, in compliance executions... Can ONLY be found on certain electronic exchanges. (3) People data-mining NYSE data for "patterns"... Are unknowingly crunching out-of-sequence data. This is the reality... White Collar Crooks are much smarter than lowly Technocrat Regulators. Evolve or die.