From the Los Angeles Times:
The study found that people's evaluations of their lives improved steadily with annual income. But the quality of their everyday experiences -- their feelings -- did not improve above an income of $75,000 a year. As income decreased from $75,000, people reported decreasing happiness and increasing sadness, as well as stress. The study found that being divorced, being sick and other painful experiences have worse effects on a poor person than on a wealthier one.
The researchers do point out that people earning $75,000 a year would not necessarily be unhappy to receive a raise.
According to the U.S. Census, median household income was $50,303 in 2008.
Photo (cc) by Flickr user Kevin Dooley