Sorry flipper et al - the Brexit is bogging me down at work. I have spent no time looking at the volume action thurs/fri but the russell rebalancing does have a lot to do with it. The price not moving for much of friday has a lot to do with with the market maker matching up buys and sells and trying to determine where the closing price should be due to the rebalancing. Flip, regarding your specific after hours broker action, I did see most of the volume came from UBS on Friday but that didn't include after hours. I need to look into how I can see where after-hours is coming from. I'm hoping to not be as busy tomorrow...
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