Insurers charge different prices for what looks like the same risk, and the differences are not arbitrary. They come from filed rating plans that regulators review before use.
Rates are filed rather than simply set
In most states an insurer must file its rates and rating rules with the regulator, showing how the price for any given applicant is calculated.
The filing includes base rates, the factors applied for each rating variable, and the actuarial justification supporting both of them.
Prices therefore follow a documented formula rather than a judgement made at the point of sale.
An agent quoting a price is applying that formula rather than negotiating one, which is why the same insurer quotes the same figure through every channel.
Each insurer weighs the same variables differently
Two companies may both use age, location, prior claims and coverage limits while assigning quite different multipliers to each of them.
An insurer whose own experience shows a variable predicts losses strongly will weight it heavily, and another with different data will not.
The result is that one company can be cheapest for one profile and among the most expensive for a neighbouring one.
No insurer is broadly cheap or broadly expensive, which is why advice to shop around holds even for people who shopped a few years ago.
Underwriting appetite shapes the price further
Insurers target the segments they believe they price well, and they discourage the rest through higher rates rather than through outright refusal.
A high quote is often a signal that the applicant sits outside the company's intended book rather than that the risk itself is poor.
Shopping across several insurers surfaces this quickly, because appetite varies far more between companies than actual risk does.
Approval mechanisms differ by state
Some states require prior approval before a new rate can be used, while others allow use on filing with the review conducted afterwards.
Where approval is slow, filed rates can lag current costs, which later appears as a single larger increase rather than a gradual one.
These rules differ by jurisdiction and change over time, which is part of why the same insurer prices differently across state lines.
Filings are public documents
Rate filings are generally available through state insurance departments, and they set out the rating factors an insurer applies to each variable.
They explain increases that arrive with no change in the policyholder's own circumstances, since a base rate change affects everyone in the class at once.
Reading the filing behind a renewal increase turns an unexplained number into a traceable one.
It also shows whether the increase came from a general rate change or from a factor specific to the policyholder, which are two very different problems.