In my homecountry JWs resemble the average general popoulation, perhaps not too well represented among the very affluent, but definitely average.
A study from America, shows that average household income among american JWs is slightly below the average, but considering that quite a few work less than full time and the percentage of hispanics and afro-americans are substantially higher than national average, this is considered good. Also, the number of American JWs that owns their own house is exactly the same as the national average.
I have travelled extensively, and visited JWs in many countries, definitely also average... Please bear in mind that in many underdeveloped countries, the number of literate witnesses is way above the national average and thus it might be that their socio economic status might be better..
The link to the study is provided here:
http://www.religionomics.com/old/erel/S2-Archives/Iannaccone%20-%20JW%20Growth.pdf