The map looks interesting and looks believable, but I tend to give that sort of data a pinch of salt. As a gut reaction, I'd have expected areas of London to be amongst the poorest.
Also, what exactly has been measured?
We had that fantastic statistic the other day in the Libertarian thread that Saudi Arabia was more free than Portugal.
But perhaps, like a politicians lies and dalliances they don't need to be factual, they just need to feel true.