Wednesday, November 17, 2010


The High Cost of High Frequency Trading

I have personally seen markets change when computers enter and cancel orders at high speed and through my contacts in the trading business I know that a lot of traders have left the business or had to alter their trading style because computers have made market making impossible for the individual. That loss of liquidity, I believe, will be disastrous for markets when volatility causes the HFT firms to unplug their machines. (see the Flash Crash)

Let's say that there is a buyer willing to buy 100,000 shares of BRCM with a limit price of $26.40. That is, the buyer will accept any price up to $26.40.

But the market at this particular moment in time is at $26.10, or thirty cents lower.

So the computers, having detected via their "flash orders" (which ought to be illegal) that there is a desire for Broadcom shares, start to issue tiny (typically 100 share lots) "immediate or cancel" orders - IOCs - to sell at $26.20. If that order is "eaten" the computer then issues an order at $26.25, then $26.30, then $26.35, then $26.40. When it tries $26.45 it gets no bite and the order is immediately canceled.

Now the flush of supply comes at, big coincidence, $26.39, and the claim is made that the market has become "more efficient."

Nonsense; there was no "real seller" at any of these prices! This pattern of offering was intended to do one and only one thing - manipulate the market by discovering what is supposed to be a hidden piece of information - the other side's limit price!



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