I grew up surrounded by knitting and dressmaking patterns. These were the standard sizes in the '70's listed as size, bust, waist and hips. Each measurement on the next size up was 2 inches larger.
At 5 foot 3 and weighing 8 stone, my stats were 33, 28, 35. I was just an ordinary size, definitely not seen as skinny. Thing is, these measurements have stuck with me, so nowadays if anyone says size whatever, these are what I still automatically think of.
10 = 32 - 24 - 34
12 = 34 - 26 - 36
14 = 36 - 28 - 38
Then I think anything over that was frumpy and was sourced in the Evans Outsize shop, yes, it was really called that. I can remember my Granny remarking on a family member being a "really big girl, 44 inch hips".
If you look at Victorian or Edwardian clothing, they seem to make the 1970's clothes look enormous in comparison.
These days apparently, the average woman's shape has changed to a thicker waistline. Perhaps now I'll be an average shape 
I do think it would be a lot more helpful on threads like this and easier for comparison, if alongside height and weight and vanity size, people listed their bust/waist/hips measurements, although that may be a step too far, I'd not like to list mine right now 