What it means
Insurance pricing is informed guesswork about the future, and the burning cost ratio is one of the plainest ways to use the past. It takes the losses a block of business has actually produced over several years and divides them by the premium or exposure base over the same period.
The result is a percentage showing how much of each premium dollar was consumed by claims. It matters because it is cheap to calculate and hard to dismiss.
A ratio built on five years of real claims gives a negotiating anchor that neither the insurer nor the reinsurer can wave away as modelling guesswork. Both sides then argue about adjustments rather than about the starting point.
In excess of loss reinsurance the version used is the burning cost of the layer. Only losses that would have reached above the retention count in the numerator, so a layer that has never been hit shows a burning cost of zero and has to be priced on judgement instead.
That is exactly where the method runs out of road. A raw burning cost is not a price.
Underwriters load it for claims that have happened but are not yet reported, for inflation in future claim costs, for expenses and brokerage, and for the profit margin the capital requires. The loaded figure becomes the rate applied to next year's subject premium.
Trending matters as much as the ratio itself. Claim amounts inflate faster than general prices in many lines, especially where medical costs or court awards are involved, so a plain five-year average understates what the same events would cost next year.
Good practice is to restate each older year at current cost levels before averaging. The closest relative is the loss ratio, which looks similar but is a different tool.
A loss ratio usually covers a single policy year on a direct book, while burning cost deliberately spans several years to smooth out volatile experience. Use burning cost where claims are infrequent but large.
In practice
Real-world examples.
Example
A reinsurer quoting a layer on a regional insurer's motor book adds up losses above $500,000 over six years and divides by the premium that book produced, arriving at a burning cost of 18%. After loading for unreported claims, expenses and profit, the quoted rate becomes 25% of subject premium.
Example
A hospital group self-insures the first slice of its liability exposure and tracks its own burning cost ratio each year. When the figure climbs from 31% to 44% over three years, the board funds a patient safety programme rather than simply raising the internal charge to departments.
Example
A broker renewing a construction client's excess cover presents a burning cost of 9% built from seven years of claims, and argues that the insurer's proposed rate of 20% cannot be justified. The negotiation settles at 14% once both sides agree how to trend the older claims to current cost levels.
Formula
Calculation
Burning cost ratio = (total incurred losses in the period / total subject premium in the period) x 100
Worked example: a reinsurer reviews five years of a haulage fleet account. Subject premium over the five years totals $10,000,000 and incurred losses above the $250,000 retention total $2,400,000. Burning cost ratio = 2,400,000 / 10,000,000 = 0.24, or 24%. To turn that into a price the reinsurer divides by its target loss ratio of 0.75, giving 24% / 0.75 = 32% as the rate on subject premium. Applied to next year's expected subject premium of $2,200,000, the premium becomes 2,200,000 x 0.32 = $704,000.Case study
Seen in the real world.
Ridgeline Freight is a fictional trucking company used here as an illustrative case. It carried a $250,000 retention on motor liability and bought cover above that level, and for four quiet years its burning cost ratio ran at about 12% of a subject premium of $6,000,000 a year.
In the fifth year a single serious accident produced $2,400,000 of claims above the retention. That lifted five-year losses from $3,600,000 to $6,000,000 against $30,000,000 of premium, moving the burning cost from 12% to 20% and raising the renewal quote sharply.
The finance director accepted the increase but used the same arithmetic to make an internal case. Each 1% of burning cost was worth roughly $60,000 of annual premium, which justified a $400,000 investment in driver training and telematics. In this illustrative example the ratio worked as a management tool rather than only as a pricing input.
Watch out
Common mistakes.
- Quoting a raw burning cost ratio as the premium rate, when it still needs loading for unreported claims, claims inflation, expenses and profit.
- Averaging several years of claims without trending the older ones to current cost levels, which understates the true cost of the risk.
- Reading a zero burning cost on a high layer as evidence that the layer is nearly free, when it only means the layer has not yet been hit.
Questions
People also ask.
Over how many years should a burning cost be calculated?
Commonly three to five years for ordinary business and longer where claims are infrequent and severe, using enough years to smooth out luck without reaching back to irrelevant conditions.
How does burning cost differ from a loss ratio?
A loss ratio measures claims against premium for a single period on a direct book, while burning cost deliberately spans several years and usually counts only losses above a retention.
Can a buyer influence its own burning cost ratio?
Yes, because the numerator is real claims, so safety, training and claims handling improvements show up in the ratio and then in future pricing.
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