I've been told that the aftermarket trades are done as a rounding exercise by funds. Say they have been accumulating shares during the day with program trading and they end with 4900 or 5100. They will buy another 100 shares or sell to get 5000 and they don't care about the price.
Watch the crazy spreads and movements on the bid and ask at the EOD. Traders know that the fund may need to buy or sell shares so thats why you get the aftermarket moves.
As far as pre-market. I think its another method to acquire shares. They run it up in pre-market with 100 share trades and then watch as investors sell into the open. If you averaged it out then they may be able to end the day with more shares at a lower avg. then if they started buying at the open and ran the price up.
So both pre-market & after-market trades higher then normal trading hours indicates someone is accumulating. I know under the scenario above you could have an after market sell, but they were still accumulating during the day.
Ok, take it for what its worth.
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