Fascinating and important findings:

For example, the relationship between happiness and income is complicated, and after a point, tenuous. It is true that poor nations become happier as they become middle-class nations. But once the basic necessities have been achieved, future income is lightly connected to well-being. Growing countries are slightly less happy than countries with slower growth rates, according to Carol Graham of the Brookings Institution and Eduardo Lora. The United States is much richer than it was 50 years ago, but this has produced no measurable increase in overall happiness. On the other hand, it has become a much more unequal country, but this inequality doesn't seem to have reduced national happiness.

On a personal scale, winning the lottery doesn't seem to produce lasting gains in well-being. People aren't happiest during the years when they are winning the most promotions. Instead, people are happy in their 20's, dip in middle age and then, on average, hit peak happiness just after retirement at age 65.

People get slightly happier as they climb the income scale, but this depends on how they experience growth. Does wealth inflame unrealistic expectations? Does it destabilize settled relationships? Or does it flow from a virtuous cycle in which an interesting job produces hard work that in turn leads to more interesting opportunities?