You might think that richer countries are happier. But there's actually no correlation beyond about $10,000 per capita income. See how each country compares on this scatter chart. One surprise is that Vietnam, with a per capita income of less than $5,000, has been just as happy as France, with a per capita income of about $22,000. The happiest country surveyed was Puerto Rico. The unhappiest were Indonesia, the Ukraine, and Zimbabwe. Within Europe, the happiest countries were Denmark, Ireland, and Iceland.
All that data comes from the World Values Survey. You can play around with the dataset online. (Great for a class project, kids.) And definitely check out the Inglehart-Welzel Cultural Map of the World and the other graphs that cluster cultural values by nation, all to be found by clicking the "Findings" tab. See how life satisfaction correlates with democracy and other ideologies. North America, for example, is more traditional than Northern Europe. Relatively speaking, the miserable former Soviet bloc focuses more on survival than on self-expression.
For those with a longer attention span, it's worth reading Beyond Money, the most authoritative scholarly summary; 300 academic studies on happiness packed into 25 pages. To see how the "satisfaction index" has changed over your lifetime, check out the graph on page three. Though the GDP has tripled, the average person is no more contented with life now than the average person was in 1950.