There is not a standard, it is all personal taste with the gunbuilder.
Thank you. I've got all of the other dimensions established; I just wonder what range of widths might be typical. I never see pictures of stocks where the camera is looking down on the comb. It seems there should be some apparent taper from the top of the buttplate to the (point of the) comb/wrist area.
That point is usually called the "nose of the comb" and as Jkob said, there is no standard... Europeans tend to make them more severe (sharper) where the American look tends to be rounder and more full.