Please forgive me if the terms aren't 100% correct.
Different insurers do their calculations differently, but this is my understanding of the basic process:
No Claims Discount, normally rated in years, is a discount given which insurers apply to your actual calculated 'rate' or risk.
Different insurers use different amounts for the years earned - no consistency.
Your Rate or Risk is calculated based on some industry calculations tailored by individual insurers, which consider what is the likelihood of having to pay out to you, and is based on many factors including age, locatio