The loss ratio is the percentage of premium an insurer pays out in claims: incurred losses divided by earned premium. A 65% loss ratio means the insurer pays 65 cents in claims for every premium dollar earned, leaving 35 cents to cover expenses and profit.
Why It Matters
Loss ratio is the single most-watched underwriting metric in insurance — it's how carriers evaluate whether a line of business, a distribution channel, or an individual underwriter is pricing risk correctly, and it directly drives rate filings with regulators. A persistently high loss ratio forces a carrier to either raise rates, tighten underwriting, or exit a line.
How It Works in Practice
- 1Incurred losses = paid claims + change in reserves for claims not yet fully settled
- 2Earned premium = the portion of written premium that corresponds to coverage already provided during the period
- 3Loss ratio = incurred losses ÷ earned premium, typically tracked by line of business, geography, and distribution channel
- 4Loss development (how loss ratios change as claims mature and are re-estimated) is tracked separately since initial reserve estimates are frequently revised
Common Pitfalls
Loss ratio alone ignores expenses — a line with a low loss ratio can still be unprofitable if acquisition and administrative costs are high, which is why it's usually paired with the expense ratio into a combined ratio
Immature accident years understate ultimate loss ratios for lines with long claim tails (liability, workers' comp) since not all claims have been reported or settled yet
A single catastrophic event can distort a period's loss ratio badly enough that underlying trend analysis requires excluding or separately tracking cat losses