territorial and class plan rating

Two drivers can be identical in age, car, and record, yet one lives in a dense city where cars get stolen and fender-benders are constant, and the other in a quiet rural county. They do not cost the same to insure. Territorial rating captures the where; the class plan captures the who and what. Together they are the structured set of rules that turn a customer's characteristics into the relativities applied to the base rate.

Territorial rating groups geographic units (postcodes, counties, defined zones) into territories with similar loss experience, each carrying a relativity — say 1.30 for a high-theft urban zone, 0.80 for a low-density rural one. Because any single small area has thin, volatile data, territories are smoothed and credibility-weighted, sometimes using spatial techniques that borrow strength from neighbouring areas. The class plan is the wider scheme of all the other rating variables and their levels — age, vehicle, usage, prior claims — and the rules for combining them. A class plan defines, for example, which combinations get which relativity and how they multiply together in the rating algorithm.

These two structures are where fairness, competitiveness, and regulation meet on the ground. A well-built class plan lets an insurer attract the risks it understands and price each fairly; a poorly built one invites adverse selection and complaints. Territory is especially sensitive: it correlates with income and demographics, so regulators in many places scrutinize or restrict how granular territorial rating may be, and some require that territorial definitions not act as a proxy for prohibited characteristics. The actuary must balance statistical accuracy against these legal and social limits.