[ajross]

The cynical answer is that you specialize in post-hoc analysis like this. Predictions, after all, can be wrong. :)

This is true in general obviously, but investing specifically is filled with explanations like this that make sense only in hindsight.

[mikeyouse]

I completely agree in most cases, however the Reuters article I linked was written earlier this week. Some market conditions necessitate a big swing in prices -- though guessing which direction prices will swing can be tricky.

If you wanted de-risk your position, you could set up an option straddle or just sell your shares before the announcement and then buy them again next week.