50% of happiness is genetic?

[notoverrated]

"Lyubomirsky and her colleagues analyzed studies on identical twins and other research and came to the conclusion that happiness is 50% genetic, 40% intentional and 10% circumstantial. "Half of your predisposition toward happiness you can't change," she says. "It's in your genes. Your circumstances where you live, your health, your work, your marriage can be tough to change. But most people are surprised that circumstances don't account for as much of their happiness as they think."

http://www.latimes.com/la-he-happy8-2008sep08,0,6171435.story