Cost-Based Pricing of Individual Automobile Risk Transfer: Car-Mile Exposure Unit Analysis

Every mile traveled by a car transfers risk to its insurer. This paper posits that the product of a cents-per-mile rate based on class experience and the miles recorded on the car’s odometer appropriately earns prepaid premium while the car is driven. Operation of a practical car-mile system is described briefly. To test the competing idea that driver-record pricing responds to known large differences in risk transfer, a model used to validate claim free discounts is reexamined with the car-mile as the measure of individual cost. Driver-record pricing is found to inflate car-year price-tocost differences. Consequences of accident rate variability for a car-mile system are reviewed. The per mile cost of individual risk transfer is a class property because of the random nature of accidents. Driver-record pricing attempted on a per mile basis would amplify differences within classes.