I think we might be here all day if we keep discussing the rest of the thread so I'd rather discuss this material if you don't mind. I don't think you need comparisons of utility to know that poor people have higher marginal utility. That's an assumption that will get us closer to the right answer than ignoring the distribution. I agree with you about GDP, but consumption is the ultimate goal of production and it moves very closely with GDP. In other words, all the empirical work could be done for consumption instead of just GDP and it would work just as well.