When you're buying a bottle of wine for a friend's party, you don't want to embarrass yourself by going too cheap. But you also don't want to spend more than you need to. So how do you figure out what to buy?

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Well, someone came up with a simple way to calculate how much you should spend: Just estimate the household income of the people throwing the party, and then divide it by 10,000.

So if your friend makes $50,000 a year, a $5 bottle is probably fine, if they make $80,000, look for an $8 bottle or if it's a couple who make a combined $120,000 a year, it should be more like $12.

That way, the wine you buy should be right around the same price as the wine they bought for the party.

Obviously it means you have to speculate on how much money your friends make. If we're being honest, you probably do that anyway.

Read more at 11 Points.