why volume doesn't translate to price movement at marketclose

[ericcccc 0]

Hi community,

just want to ask a question related to volume. I often see a huge volume coming in at market close. For example, there was 422k shares traded at market close for BABA on 4/9. However, these volume volume doesn't actually translate to price change. If you take a look at the price, it only changed less than 0.1$ . This often happens and is definitely not specific to this stock, this day.

I am wondering, what happened at that time ? 

 

[ericcccc 0]

Thanks @peterB for the illustration. I get that part that slightly more sellers moved the price a little lower. It's more understandable during the day since the market is very active.

What I don't understand is, why these sellers and buys are having tacit understanding and act on almost same time particularly at market close, at the very last minute ?  Is this something related to arbitrage or  automatic trading done by market makers ? The only thing I can think of is market makers are selling and buying at the same time so essentially they are playing with themselves, or playing with another market maker.