How your car insurance rate is calculated

The four groups of factors

Every carrier weighs these differently — that is exactly why the same driver gets different numbers from different companies — but they all weigh roughly the same things.

• The driver. Age, years licensed, marital status, and in most states an insurance score. Tickets, at-fault accidents and claims, over a look-back period that is not the same at every carrier.
• The vehicle. Year, make, model and trim. What it costs to repair, how often that model is stolen, how well it protects the people inside it, and what its safety equipment is.
• The coverage. Your liability limits, your deductibles, and every optional line you keep or drop.
• Where it lives. Garaging ZIP code, not where you work. Claim frequency, theft, weather and repair costs in that ZIP.

The one most people underrate: continuous coverage

How long you have been continuously insured, and at what limits, is one of the largest single credits on a car policy. A driver coming off a lapse pays noticeably more than the same driver with three unbroken years — same car, same record.

It is also the factor most often mishandled, because the online form asks one blunt question about it and moves on. Whose policy it was, the exact dates, and the reason for any gap all matter, and at some carriers a gap under thirty days is treated very differently from a gap over it.

What you can change, roughly in order of effect

• Your limits and deductibles. The most direct lever, and the one with a real trade-off attached.
• Which carrier you are with. The same profile is priced very differently across companies, and the spread is usually wider than anything else on this list.
• Discounts you qualify for and have not claimed.
• How you pay — paid in full and automatic payments are credits at most carriers.
• Which vehicle you buy next. Two cars in the same price bracket can be a long way apart on insurance.

What you cannot change quickly: your record, your address, and how long you have been insured. Those improve with time, which is why a policy is worth re-shopping every year rather than once.

Why a ticket costs more than the ticket

A moving violation stays in the rating for years, not months — commonly three, sometimes five. The surcharge is applied at every renewal in that window, so the real cost of a ticket is the fine plus several years of a higher premium.

It is also a place where carriers differ sharply. One company surcharges a first minor violation heavily; another barely notices it. Which is which is not published, and it is most of what an agent who places this business every day actually knows.

Insurance scores, briefly

Most states allow carriers to use a credit-based insurance score as one rating factor. It is not your credit score and it is not used the same way, but it is built from the same file, and it does move premiums.

Neither Texas nor New Mexico prohibits it. If your credit has improved since the policy was written, that is a real reason to re-shop.