Auto Insurance Pricing: Rating Variables and Territory

Key Rating Variables

Personal auto insurance pricing uses numerous rating variables to segment risks. Driver-related factors include age, gender (in states where permitted), marital status, driving record, and years of experience. Vehicle-related factors include make, model, model year, vehicle use, and annual mileage. Policy-related factors include coverage limits, deductibles, and multi-policy discounts. Credit-based insurance scores are significant predictors in most states, though their use remains controversial. Actuaries fit GLMs to large datasets to estimate the independent effect of each rating variable on loss frequency and severity.

Territorial Rating

Territory is among the most powerful rating variables in auto insurance because loss costs vary dramatically by geography. Urban areas have higher collision frequency due to traffic density, while rural areas may have higher severity due to higher speeds. Theft rates, litigation environments, and weather patterns all vary by location. Actuaries define territories using ZIP codes, counties, or custom geographic units and estimate territorial relativities using credibility-weighted combinations of local and statewide experience. Spatial smoothing techniques help stabilize estimates for areas with limited data while preserving meaningful geographic variation.