Kottke has a link to another interesting article. This one concerns the difference in earnings related to height, weight and beauty (which goes some way to explaining why I earn so little). There are some big charted differences. I would like to point out, however, that the conclusions that Kristie Engemann and Michael Owyang (I've removed their middle initials, what is it with using your middle initial, either all initials or none) draw lack an obvious one as far as I can see.
I agree that self-esteem, health and discrimination probably play a part, but they also state that people who are taller at age 16 generally earn more than others. Well, I always remember reading that each generation is taller than the previous one. This is because diet improves over time. So, could it not also be true that the taller people come from families that can afford a better diet, or are more aware of providing a better diet. Now, making some, admittedly wild, leaps, but would it not be possible to assume that a better diet suggests the family's economic state is better, and, possibly, that they come from a famiy that has, therefore, a history of earning higher than average wages? So these people may be genetically and socially more advantageous from the start, rather than it being related to their physical traits.