How insurance works: premiums, pooling and risk
Why many people paying a little protects each person against a large loss — and what that means for your premium, your deductible, and the policy you choose.
The core idea: sharing risk
Insurance works because most people, most of the time, do not suffer a large loss. By collecting small, regular payments — premiums — from many people, an insurer builds a fund large enough to pay the few who do suffer a loss. This is called risk pooling.
For example, suppose 10,000 homeowners each pay £200 a year. The fund holds £2,000,000. If 20 homes are seriously damaged that year and each claim costs £80,000, the fund pays out £1,600,000 — and still has a surplus. Each homeowner transferred a £80,000 risk for just £200.
The OECD Insurance and Private Pensions data shows how premium income and claim costs are balanced across different markets globally.
What sets the price of your premium
An insurer must set premiums that, in aggregate, cover the claims it expects to pay plus its operating costs. To do this it estimates your individual risk using rating factors — characteristics that predict how likely and how costly a claim will be:
- For motor cover: age, driving record, vehicle type, annual mileage, location.
- For home cover: rebuild cost, postcode, construction type, flood or subsidence risk.
- For health cover: age, location, plan tier, tobacco use (where permitted by law).
The NAIC consumer portal lists which rating factors are permitted in each US state. In the UK, the FCA's motor insurance guidance explains how pricing must be fair under FCA rules.
The deductible: your share of the risk
Most policies include a deductible (called an excess in the UK and Australia) — the first portion of any claim that you pay yourself. Choosing a higher deductible usually lowers your premium, because you are absorbing more of the risk.
This trade-off is explored in detail in our guide to deductibles and out-of-pocket maximums. You can also use the deductible trade-off calculator to see how many claim-free years a higher deductible needs to pay back the premium saving.
The limit: the insurer's share of the risk
Every policy has a limit — the maximum the insurer will pay. For home insurance this is the rebuild cost; for motor it may be the vehicle's market value; for health it is the annual or lifetime maximum. A loss above the limit is your responsibility.
Understanding limits is part of reading the five parts of every policy, particularly the declarations page and the insuring agreement.
Exclusions: where the pool stops
Not every loss is included in the pool. Exclusions describe events and circumstances the insurer has decided to price out of the policy — because they are too predictable, too catastrophic, or involve moral hazard. Our guide to exclusions explains the most common types and how to check them.
Where to find this in your policy
Policy sections
- The Insuring Agreement describes exactly which events the insurer will pay for.
- The Declarations page shows your premium, limits and deductible.
- The Exclusions section lists what is not covered.
- The Conditions section sets out your obligations — including paying the premium on time.
See our guide to the five parts of every policy for a full walkthrough.
Questions about this topic
Frequently asked questions
- Premiums are set for a pool of policyholders, not for you individually. If the cost of claims across the pool rises — because of inflation, weather events, or more accidents — the premium rises for everyone. The Insurance Information Institute explains the factors that affect motor premiums in detail.
- The premium is what you pay to keep the policy in force — a regular fee whether or not you claim. The deductible (called an excess in the UK and Australia) is the first portion of any claim you pay yourself. See our guide to deductibles and out-of-pocket maximums for worked examples.
- A no-claims bonus (or no-claims discount) rewards you individually for not claiming, reducing your share of the pool's cost. It doesn't change how pooling works — it just means lower-risk policyholders pay proportionally less. The Association of British Insurers (ABI) publishes data on how no-claims discounts are applied.
- Insurers use rating factors — age, location, claims history, type of cover, sum insured — to estimate the likelihood and cost of a claim. People who are statistically more likely to claim pay more into the pool. The NAIC consumer portal lists the rating factors your state insurer is allowed to use.