Definition:Frequency
📊 Frequency measures how often claims or losses occur within a defined period and exposure base, serving as one of the two fundamental building blocks — alongside severity — that actuaries use to model expected losses in insurance. Expressed as a rate (for instance, 5 claims per 100 policy-years), frequency gives underwriters and pricing teams a quantitative handle on how likely a given peril is to produce a loss event for a defined pool of risks.
🔢 Actuaries calculate frequency by dividing the number of claims by the number of exposure units — which could be policies in force, vehicle-years, payroll dollars, or any other measure appropriate to the line of business. In auto insurance, frequency might be expressed as collisions per 1,000 insured vehicles; in workers' compensation, as injuries per million payroll dollars. Trend analysis tracks whether frequency is rising or falling over time, driven by factors like distracted driving, safety regulations, or economic cycles. Catastrophe modelers distinguish between attritional frequency (routine, high-count losses) and catastrophic event frequency (rare but correlated losses), since each demands different modeling approaches and reinsurance strategies.
📈 Understanding frequency is indispensable for accurate ratemaking and reserving. A sudden uptick in claim frequency — even if individual severity remains stable — can erode a loss ratio rapidly because it compounds across an entire portfolio. Carriers monitor frequency trends at granular levels (by geography, class code, policy vintage) to catch emerging problems before they materialize in aggregate results. For insurtechs building usage-based or telematics-driven products, real-time frequency data from connected devices creates opportunities to re-segment risk more dynamically than traditional annual reviews allow.
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