anybody know about marketing/advertising terminology?

Specifically these terms regarding readership class (say for the readership of a magazine):

AB
C1
C2
DE

I believe it refers to level of income but wonder if there's a specific breakdown for it at all?

TIA!

i'll ask hubs who is in ad sales for a magazine.  BRB

Does this help?

http://www.medialive.ie/General/econ.html

from dave:

OK, these are class dermographics.

A = professionals (e.g., bankers / doctors / lawyers / people with
certified qualifications)
B = white collar (office workers)
C = Skilled manual workers (who have acquired skills, e.g., plumbers,
electricians)
D = Semi-skilled manual workers (
E = Unskilled manual workers (e.g., porters, labourers)

Sociologists have been talking for years about changing these to be more
refined, but this is the general gist.

Cool, that's sort of what I was thinking but wondered if there were income values attached to them.

Thanks to both of you (and Dave!).

I found this:

http://www.aber.ac.uk/media/Modules/aueb/comm-internet11.html

It doesn't look as though there are income levels connected.