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📊 '''Percentile''' is a statistical measure widely used in insurance to express the point in a probability distribution below which a given percentage of outcomes falls. When an insurer states that its [[Definition:Reserves|reserves]] are set at the 75th percentile, for example, it means the booked amount is expected to be sufficient to cover actual claims in 75 out of 100 equally likely scenarios. Percentiles are foundational to how the industry quantifies [[Definition:Uncertainty|uncertainty]] in [[Definition:Loss reserving|loss reserving]], [[Definition:Catastrophe model|catastrophe modeling]], [[Definition:Capital modeling|capital modeling]], and [[Definition:Risk appetite|risk appetite]] calibration — translating complex distributions into actionable thresholds that underwriters, actuaries, and boards of directors can use to make decisions.

📈 In practice, percentiles appear throughout the insurance value chain. [[Definition:Solvency II|Solvency II]] in Europe requires insurers to hold sufficient capital to survive a 1-in-200-year event, corresponding to the 99.5th percentile of the aggregate loss distribution over a one-year horizon. Australia's [[Definition:Australian Prudential Regulation Authority (APRA)|APRA]] has historically required general insurers to hold [[Definition:Claims liability|claims liabilities]] at a 75th percentile probability of sufficiency, providing an explicit margin above the central estimate. In contrast, [[Definition:US GAAP|US GAAP]] reserving conventions do not mandate a specific percentile, often targeting a "best estimate" or a level that includes a reasonable provision for adverse deviation, with the actual percentile implied rather than prescribed. [[Definition:Internal model|Internal models]] used by sophisticated insurers and reinsurers routinely produce full probability distributions, from which management selects percentiles aligned with the organization's risk tolerance — say, the 99th percentile for setting [[Definition:Probable maximum loss (PML)|PML]] limits on natural catastrophe exposures.

🎯 Communicating risk in percentile terms gives insurers a common vocabulary that bridges actuarial analysis, executive strategy, and regulatory compliance. A board evaluating whether to enter a new [[Definition:Line of business|line of business]] can compare the 95th percentile loss scenario against available capital; a [[Definition:Chief risk officer (CRO)|chief risk officer]] can report [[Definition:Value at risk (VaR)|value at risk]] and [[Definition:Tail value at risk (TVaR)|tail value at risk]] metrics anchored to specific percentiles; and reinsurance buyers can negotiate attachment points by referencing modeled return periods (the inverse of exceedance percentiles). However, percentiles also carry limitations that practitioners must keep in mind: they say nothing about the severity of outcomes beyond the chosen threshold, they are only as reliable as the underlying model and data, and different distributional assumptions can produce materially different percentile estimates for the same portfolio. Despite these caveats, the percentile remains one of the most widely understood and practically useful risk measures in global insurance practice.

'''Related concepts:'''
{{Div col|colwidth=20em}}
* [[Definition:Value at risk (VaR)]]
* [[Definition:Tail value at risk (TVaR)]]
* [[Definition:Capital modeling]]
* [[Definition:Loss reserving]]
* [[Definition:Probability of sufficiency]]
* [[Definition:Solvency II]]
{{Div col end}}

Definition:Percentile - Revision history

PlumBot: Bot: Creating definition