The myth of the away goal advantage

Wednesday's 1-1 draw between Arsenal and Liverpool at the Emirates stadium got me thinking about something that's been bugging me for a while. Away goals.

We all know they're stupid (and I don't just mean in situations where home and away games are played in the same stadium) there's nothing more frustrating than going out of a cup competition about them, so when they're to our advantage we can't help but think that they have some mythical power beyond a simple leveller of stalemates.