Quote from hayman:
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1) Specialists "pennying" front-running activity seems to be on the rise, since market liquidity has dried up of late. Although NYSE Open Book quotes are on a 10-second delay, market orders that are "front-run" by Specialists (by a penny), rarely, if ever, appear as entered orders on the NYSE Open Book. This results in Specialists "jumping in front" when it is advantageous for them, and diminishes the usefulness of the supply/demand information provided in the Open Book, and provides the Specialist with a tremendous advantage. This activity is running rampant these days - the invent of decimalization has been a real boon
for the Specialist; not the trader. The so-called "price improvement" that NYSE allows for, provides for penny improvements for those who are already willing to pay the "market" price for a stock, and causes "price disimprovement" for those that are posting limit orders, and are jumped in front of. This clearly disrupts the laws of supply and demand in the marketplace, and diminishes the usefulness of placing
limit orders. This results in diminished confidence in the marketplace by those placing limit orders, which will inevitably result in fewer limit order being placed. This will ultimately (and has already) diminished the liquidity in the marketplace.
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I am not trying to defend the specialist, but sometime it could be a broker just standing at the post waiting for stock to come in before making a purchase. Thus, you would never see him in open book. For example, if a Goldman house broker is standing at the Disney post with 250,000 shares to buy. He will just stand at the post all day and wait for stock to come in for sale. Then it could be him pennying you (or anyone). Since he is standing at the post representing his order, there is no incentive for him to put anything in the open book. Thus, you will never see him unless you get a "look" from the floor.