Definition:Burning cost ratio
🔥 Burning cost ratio is a retrospective measure of loss experience that compares actual historical losses to the premium base or exposure measure over a defined period, serving as a foundational input for pricing excess-of-loss reinsurance and high- attachment-point insurance layers. Unlike frequency-severity models or stochastic simulations, the burning cost approach relies on observed data — what has actually "burned" through a portfolio — to estimate the rate needed to cover expected future losses at a given layer. It is one of the oldest and most intuitive actuarial tools in the reinsurance pricing toolkit.
📐 To calculate it, an actuary or underwriter collects historical losses that would have penetrated the layer in question, adjusts them for loss development and inflation (known as "trending" and "developing" the losses), and divides the adjusted losses by the corresponding subject earned premium or an appropriate exposure base. The result is expressed as a percentage — for instance, a burning cost of 12% means that, based on historical experience, losses at the relevant layer have averaged 12 cents for every dollar of subject premium. Reinsurers then load this figure for expenses, profit, and a risk margin to arrive at a quoted rate. The method works best when the loss history is credible and the portfolio composition has remained reasonably stable; for lines with sparse large-loss data or rapidly changing risk profiles — such as cyber — burning cost analysis alone may be insufficient and is often supplemented with exposure-based models.
💡 Market practitioners value the burning cost ratio for its transparency and simplicity: both cedants and reinsurers can examine the same historical loss record and debate adjustments openly, which facilitates negotiation. During renewal discussions, a cedant with a favorable burning cost trajectory can argue for rate reductions, while a reinsurer facing deteriorating burning costs has concrete evidence to push for increases. The metric also appears in experience-rated contracts, retrospective rating arrangements, and sliding-scale commission structures, where actual loss experience directly influences the final economics of the deal. Across markets from London to Bermuda to Singapore, the burning cost ratio remains a common language that bridges different actuarial traditions and negotiation styles.
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