In economics we think that happiness increases with lifetime wealth, albeit at a decreasing rate. But recent research on happiness fails to show a steep gradient between incomes and self-reported life satisfaction. But this work has typically focused on rich countries. In a recent paper, Angus Deaton uses Gallup poll data for a large number of countries and uncovers--to my surprise, at least--that people in poor countries are indeed less "happy" on average than people in rich countries.
Here is the relationship, broken down by age group.
So much for the romantic idea of the poor but happy peasant, in communion with his natural environment...
But note also some of the interesting anomalies. For example, Indians are a lot happier than the Chinese, despite having lower incomes on average. Maybe the influence of all those Bollywood movies? And Pakistanis are significantly happier than either. One wonders what they are on.