On the positive correlation between alcohol use and income: I think it's because alcohol is socially disinhibitory, and expected to be that way, and this makes it socially useful for, e.g., getting information out of people that they'd usually guard. Most office politics is learned at the bar. If you ask someone, at 3:00 pm, certain pointed questions, you're a creep and a gossip. If you ask those questions after-hours at the bar when everyone's "supposed" to be drunk and loose-lipped, no one gives a shit.