Although happiness is largely up to the individual, new research shows that what's going on around you -- specifically how much personal freedom you have -- also plays a role.

In a paper published in the July issue of Perspectives on Psychological Science, lead researcher Ronald Inglehart, a professor of political science at the University of Michigan, refuted the long-held belief that happiness among societies is constant. His research concluded that significant and enduring changes in happiness can occur not only for individuals, but also for entire societies.

The study, which Seligman calls the best he's seen on happiness in five years, analyzed polls taken from 1981 to 2007 by the World Values Survey. The surveys consisted of 88 countries containing 90% of the world's population, and measured happiness and overall life satisfaction. Among the 52 countries that completed all the surveys over the 17-year period, happiness rose in 45 of them, or 86%. In six countries, it declined, and in one (Australia), levels showed no change. Overall, happiness increased 6.8 percentage points.

Inglehart credits economic development, democratization and increasing social tolerance for the happiness bump. Economic gains that bring more food, clothing, shelter, medical care and longer life can result in a substantial increase in subjective well-being for poor societies, he says.

But once a society reaches a certain threshold, further economic growth brings only minimal gains. Among the richest societies, increases in income are only weakly linked with higher levels of subjective well-being.

While economic growth helps promote happiness for some, democratization and rising social tolerance contribute even more. Democracy provides more choice, which promotes happiness. Support for gender equality and tolerance of people who are different from oneself are also strongly linked, not just because tolerant people are happier, but because living in a tolerant society enhances everyone's freedom, Inglehart says.