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At 1pm, still very low levels of algo activity today

When watching algo activity, as an indicator of direction, you really have to ignore the first hour of the day, especially the first half hour.  There's just too much noise to separate out the trading algos from the normal buy/sell activity of investors and portfolio managers.  But after about 11:45 or so, most of the activity is dominated by HFT and other algo programs which stick out from the background noise.


The chart above shows overall levels across all exchanges.  See how the spike during the 12:35 minute sticks out above the background level?  This particular spike moved SPY from 122.44 to 122.72 in 45 seconds.  In a dull market, these moves up in price caused by the algorithm typically trade back most of the move.