Another, mostly unrelated comment: the ultimatum game can actually tell you two different things. First, what divisions do people propose, and second, what divisions do people accept?

Presumably, everyone accepts fair divisions. Different groups of people have different percentages that reject unfair divisions, and different percentages that offer unfair divisions (a simplification, since the degree of fairness can also be varied). There are four potential clusters: groups that propose fair and accept unfair, groups that propose fair and reject unfair, groups that propose unfair and accept unfair, and groups that propose unfair and reject unfair. (Empirically, I believe only three of these clusters show up, but it'd take a lit search to verify that. The first two groups can be differentiated by having confederates propose unfair divisions)

These differences between people groups have real-world implications.

[edit] Note that Kaj_Sotala has found at least one paper on the subject.