When there's no base (or 'cause') built up, the 'effect' tends...

When there's no base (or 'cause') built up, the 'effect' tends to be small or short-lived. Banks need to build a position before they begin the mark up. Accumulation takes them many months or years of sideways action to complete. A sudden spike in the middle of a down trend can still continue to the upside, it's just much less likely.

Many banks know ahead of time what a company will announce. There's no such thing as a secure IT department.