[ljordan]

In the study I heard about from a family member it correlates strongly up to a threshold, say $90,000 for a family of 3-4 living in the midwest (ex-Chicago, etc.), but thereafter increasing income doesn't increase happiness (and possibly erodes it).

[StavrosK]

Yes, obviously having a very low income would come with worries, but above that, as you said, there's not much correlation...

[klbarry]

Yes, what has been found is that anything below $60,000 is strongly correlated with unhappiness, but it flattens out above 60 annually. This was in a TED talk, probably one by Hans Rosling.