For the record, I am not buying into this.  I think happiness is a choice and you can have it with a little faith and any economic situation.  What I think money can buy you is ease and options.

Still, here is the latest study:

Economists believe they have discovered the higher a person's income the more satisfied they are with life. A University of Michigan study found the richer people are the happier they are.

People were asked to rate their levels of happiness and their income was recorded. Everyone with an income of over $400,000 a year or more classed themselves as “very happy”.  The University of Michigan study found that all those earning $95,000 a year or more also described themselves as either very or fairly happy.

Begs the question, did they ask anyone who makes less than that?