There's data showing that in the USA, the happiness gradient increases as people live further out - in the rural areas (Okulicz-Kozaryn & Berry, 2011). Having said this, the happiness of Americans is also known to plateau at a certain wealth level, and it seems that there's some sort of correlation between urban wealth and happiness - to a point, which then reverses, seeing people off into the periphery again (Montgomery 2013). This may explain why the US situation is contradicted in much of Europe and Asia. But what drives this? Is there a way we can locate this magical threshold? And what does it have to do with the city, with suburbia and rural and remote areas? Is it the quality of the environments and what they offer inhabitants?
It's also interesting that the charter of New Urbanism appears to tackle this issue by making cities better for inhabitants. Does this raise the threshold? (CNU., 2001)
There are also neural correlates that are being discovered that fascinate me - especially in Europe, where this phenomena is being taken seriously. Really interesting correlates, that have implications for mental health (Pedersen, Mortensen & Preben, 2001;Haddad, Schafer, et al., 2014). Oft times this data is only taken from an isolated city or rural area, and therefore may be tainted by uncontrolled variables, like the quality of social housing or by the dominance of a single industry.