[anonymous5133]

What I always thought to be interesting is by analyzing those pre-announcement movements. We all know there are always people trading on insider information so it would be possible to use those pre-announcement movements to your advantage. If you see the stock price dropping before the announcement, then best to unload your shares or vice versa.

[AznHisoka]

This doesn’t work because there is no insider trading in most cases, and even if there were, you might be fooled by mass idiots trading the opposite directon of the insider.

[GoMonad]

As an example why it might drop (or rise) with high volume: firms could be "derisking" before earnings.