According to Robert Frank increases in prosperity improve how the poor are treated, are good for the environment, contribute to workplace safety, and free people for additional time (if they want it!) with their families. But most of all, it makes "premature" death more rare. Prosperous people may not experience themselves as more happy, but that fact is deceptive. Happiness can be found among paraplegics and prisoners in concentration camps, but that doesn’t mean that those people wouldn’t choose better circumstances for themselves if they could. Happiness doesn’t correlate well with prosperity or its absence, in my view, but it may correlate negatively with the opinion that you some right to it.