First off, we should say that Sonja Lyubomirsky, the UC Riverside professor who wrote the 2008 book The How of Happiness, cautions that the figures on this chart are meant to be a rough estimate, not a definitive description of the origins of happiness. But in her book, she writes that research on twins has found that our genes may determine an innate baseline for how happy we'll be during our lives. Lyubormirsky and her colleagues, Ken Sheldon of the University of Missouri and David Schkade of UC San Diego, hypothesize that this genetic set point accounts for about 50 percent of our happiness.
Next, she argues that around 10 percent of our happiness is likely based on our circumstances, basing that estimate partially on a study that showed that Americans who earn more than $10 million every year are only slightly happier than non-wealthy office or blue-collar workers. By these estimates, Lyubormirsky writes, that leaves 40 percent wide open. Again, these are estimates and arguments, not rock-solid science. But there's something very, well, happy about the idea that a big chunk of our potential well-being might be under our own control.