The volume of the day including pre and post: ~122M
The volume in that 5 sec encompassed 17/122M= 14% of the trading volume of the day.
Can anyone try to explain this phenomenon?
Some possibilities I think of:
- Day traders taking profits
- Hedge funds adjusting positions but don't want to plummet the price
- Unheard of ETFs emulating the closing price
None of these fully explain it, because why would they intentionally wait till the market close to start/close positions when they might run into the risk of lower liquidity, higher price volatility?
Updated: I checked with the tape and it was due to one single transaction (the time is in PT, NOT ET):