Also keep in mind that patterns can, and will, be affected by the shell/loading used in it. With the same constrictions, varying the load can vary the percentages of the patterns considerably.
I do understand what Karl is trying to determine. Here's Hallowell's ideas on it. By giving a range for each, Hallowell is allowing for variances in choke profile and loadings used. Very smart, IMO.
http://www.hallowellco.com/choke_chart.htm
Stan