I'm using the Buhlmann Straub credibility model for a fleet portfolio I'm working on and I'm getting what I think is a very high weight even given the size of the fleet i.e. 51% applied to experience when total vehicle years in last 5 years is 39. My k parameter is 5.64 and I use claims in the formula w/(w+k). Just some general questions about this... I am including policies with 20+ vehicles in the model. I presume any fleet with sub 20 vehicles should be exposure rated. I know this isn't clear cut and it depends on other factors but I'm a bit dubious about using this model given the high weight I'm getting. In my last company they used the formula (min(n,1000)/1000)^.5 to get Z i.e. 1000 years of exposure in the last 5 years would imply 100% experience rating. Unfortunately there are no practical examples (applied to commercial fleet) this in the literature I've read about BS. Any help would be much appreciated!
