The map shows average wages by constituency, according to the most recent ASHE figures that are available.
The first thing to note is that the figures were from a survey and while you can statistically demonstrate that surveys ought to be accurate to within a certain percentage, any sociologist with a properly functioning brain would tell you to be at least a little wary. And indeed some patterns do look a little suspect (Tatton with lower average wages than Ellesmere Port & Neston? Hmm...). Interesting, but not as reliable as would be ideal.
ASHE gets used a fair bit at my work, mostly to estimate incomes when people can't or won't (generally won't) tell us how much they earn.
I'm rather surprised that Bolton North East came out so low, given that there are some very middle-class areas in that seat as well as some very working-class areas.
