I don’t pretend to understand anything about psychology, but there is apparently a line of research into “subjective well-being” — which is, I guess, how people measure their own long-term happiness. And enough research has apparently been done to map it:

From White’s paper: “It is immediately evident that there is an effect of poverty on levels of SWB. The map itself mirrors other projection of poverty and GDP. This data on SWB was compared with data on access to education (UNESCO, 2005), health (United Nations, 2005), and poverty (CIA, 2006). It was found that SWB correlated most strongly with health (.7) closely followed by wealth (.6) and access to basic education (.6). This adds to the evidence that from a global perspective the biggest causes of SWB are poverty and associated variables.” But most research takes place in happy countries.

Thanks to Melissa Edwards for the link.