Unless you know and can manage the start weight and moisture content (That where a lot of the weight is) it sounds more like a conjecture of sorts...
Yes weight is lost and surface area is gained... however it is not always liner and without knowing what your starting with, the figures are of little use.
Just my 2 cents worth..
Oh, last but not least... It is not only water that is lost but also chaff... And some beans shead more than others so a statement of 18% is full city vs 19% full city + means little to me as there are too many other factors involved..