Dr Renwick:

What I am referring to is the guidance from the Venice Commission. My reading of that is that it implies a 10% deviation from the average. If we look at other countries, we see that in New Zealand the deviation is permitted as 5% from the average, and in Australia it is, so far as possible, 3% from the average, and not more than 10%. Therefore, numbers around 5% to 10% seem to be fairly standard. There is no answer that an academic can give you as to what is the correct number, but something in that region is appropriate.