Definition:Severity
📊 Severity refers to the magnitude of a single loss or claim in insurance, measuring how costly an individual event turns out to be rather than how often events occur. While frequency tracks how many claims arise within a given period, severity captures the dollar amount per claim — a distinction that sits at the heart of actuarial analysis and underwriting strategy. A book of business with low frequency but high severity, such as catastrophe or directors and officers coverage, demands very different reserving and pricing approaches than a high-frequency, low-severity portfolio like standard auto insurance.
⚙️ Insurers and reinsurers analyze severity by examining historical claims data, segmenting losses by line of business, geography, and peril type. Actuaries fit statistical distributions — such as lognormal or Pareto curves — to past loss amounts, then project future severity trends after adjusting for inflation, legal environment changes, and shifts in exposure. These severity models feed directly into loss ratio projections, experience rating calculations, and the structuring of excess-of-loss reinsurance layers, where attachment points are explicitly set based on expected severity thresholds.
💡 Understanding severity trends can make or break an insurer's profitability. Rising claim severity — driven by factors like social inflation, increasing medical costs, or more expensive property replacements — can erode margins even when claim counts hold steady. For reinsurance buyers, severity analysis determines how much protection to purchase and where to place layer boundaries. Ignoring a creeping upward shift in severity is one of the most common reasons underwriting cycles turn unprofitable, making this metric a critical watchpoint for chief underwriting officers and portfolio managers alike.
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