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Datalink Corporation Message Board

  • cool_scirocco cool_scirocco Nov 30, 2011 2:22 PM Flag

    Those wild and wacky algorithms

    So I decided to sell 600 shares I bought on Monday for $7.08, in order lock in a 9% gain. (not a lot, I know, but I dollar cost average in and out).

    The first attempt was to sell them at $7.79, when the bid was at $7.77 and the ask was at $7.80.

    Within 10 seconds of my order showing on LII, the computer sold a couple of hundred shares into the bid, and moved the bid/ask down to $7.75/$7.78.

    I pulled my order.

    Within three or four minutes, the computer worked it back to $7.79, and a few minutes after that, the bid/ask was at $7.80/$7.82.

    So I placed an order to sell 600 at $7.81.

    My order appeared, and within a few seconds, the computer sold into the bid and moved the best ask to below my price.

    This time I left it active, and over the next 6 minutes, it executed in small chunks.

    Really funny to me how a small order from a retail investor can cause a reaction from the computer algorithm driving most of the trading.

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