Kernrechtsfrage
Which method must be used to determine the insured person's degree of invalidity in the pension revision?
Extrahierter Entscheid
Because the insured person's self-employed income showed extreme fluctuations, neither valid income nor invalid income could be reliably determined by ordinary income comparison; the extraordinary assessment method was therefore required.
Extrahierte Begründung
The canton court's factual findings on the fluctuating business results were binding. Given the impossibility of reliably fixing comparable incomes, the extraordinary earnings-weighted activity comparison was the proper legal method, and the business profit of the transformed company could not simply be equated with personal earnings.