https://www.insurerbrain.com/w/index.php?action=history&feed=atom&title=Definition%3AAccident-year_loss_ratioDefinition:Accident-year loss ratio - Revision history2026-06-14T23:36:26ZRevision history for this page on the wikiMediaWiki 1.43.8https://www.insurerbrain.com/w/index.php?title=Definition:Accident-year_loss_ratio&diff=19090&oldid=prevPlumBot: Bot: Creating new article from JSON2026-03-16T10:07:44Z<p>Bot: Creating new article from JSON</p>
<p><b>New page</b></p><div>📊 '''Accident-year loss ratio''' is a key [[Definition:Underwriting | underwriting]] performance metric that measures [[Definition:Incurred losses | incurred losses]] arising from events that occurred during a specific calendar year, expressed as a percentage of [[Definition:Earned premium | earned premiums]] for that same period. Unlike a [[Definition:Calendar-year loss ratio | calendar-year loss ratio]], which blends reserve adjustments from prior periods into the current year's results, the accident-year approach isolates the loss experience attributable to a defined twelve-month window. This makes it one of the most analytically precise tools available to [[Definition:Actuary | actuaries]], underwriters, and financial analysts seeking to evaluate how a [[Definition:Book of business | book of business]] truly performed in a given year, free from the noise of prior-year [[Definition:Reserve development | reserve development]].<br />
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⚙️ Calculating the accident-year loss ratio requires allocating all [[Definition:Claim | claims]] — both paid and reserved — to the year in which the underlying loss event occurred, regardless of when the claim was reported or settled. For a motor insurer, for example, an accident that happened in March 2023 but was not reported until January 2024 would still be assigned to accident year 2023. The denominator uses premiums earned during that same accident year. Because many [[Definition:Long-tail business | long-tail lines]] such as [[Definition:Professional liability insurance | professional liability]] or [[Definition:Workers' compensation insurance | workers' compensation]] involve claims that develop over years, the initial accident-year loss ratio is typically based on [[Definition:Incurred but not reported (IBNR) | IBNR]] estimates that are refined as experience matures. Under [[Definition:IFRS 17 | IFRS 17]], the emphasis on measuring insurance service results by cohort year has reinforced the importance of accident-year analysis globally, while [[Definition:US GAAP | US GAAP]] statutory reporting in the United States has long required Schedule P disclosures that effectively present accident-year triangles.<br />
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🔍 For insurers and [[Definition:Reinsurer | reinsurers]] alike, the accident-year loss ratio strips away the flattering — or unflattering — effects of reserve releases and strengthening that can distort calendar-year results. An insurer might report a healthy calendar-year combined ratio while its current accident year is deteriorating, a situation that only accident-year analysis would surface. Investors, [[Definition:Rating agency | rating agencies]], and regulators therefore scrutinize this metric closely when assessing an insurer's underlying profitability trajectory. In [[Definition:Reinsurance | reinsurance]] treaty negotiations and [[Definition:Lloyd's of London | Lloyd's]] syndicate business plans, accident-year projections are foundational to pricing adequacy assessments and [[Definition:Capital allocation | capital allocation]] decisions.<br />
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'''Related concepts:'''<br />
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* [[Definition:Calendar-year loss ratio]]<br />
* [[Definition:Loss ratio (L/R)]]<br />
* [[Definition:Combined ratio]]<br />
* [[Definition:Incurred but not reported (IBNR)]]<br />
* [[Definition:Reserve development]]<br />
* [[Definition:Loss triangle]]<br />
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