Dark pool trading on private exchanges would be my guess. It's also why some stocks rarely move even when they trade much higher than their average volume.

'Market makers' (criminals) send our orders to private exchanges and trade the liabilities for the shares they sold us among themselves, in order to prevent share prices on the open market from getting to levels that would....make them uncomfortable.

The days of supply and demand based price action are long gone, and every single day in US markets is a crime scene.

Regulators and elected officials do nothing, because they're on the take. Still waiting to be proven wrong on this last point, but there is far too much evidence available now for it to be dismissed as a 'conspiracy theory'