FA-62875 / Insurance premium rating / Member archive

Workers compensation experience modification: Primary losses are split on the aggregate instead of per claim · case 05

Several moderate claims are treated as mostly excess, understating the mod.

Member previewVariant 5 · 3 implementations · 10 checks per implementation

Case contract

Input expected (cents, >0 else 'invalid expected'), split, weight W (per mille), primary_ratio (per mille of expected that is primary), ballast B, claims [[amount, 'ind'|'med']]. Medical-only claims count at 30%. Each claim splits into primary min(v,split) and excess. mod=(Ap+W*Ae+(1-W)*Ee+B)/(E+B), returned in hundredths rounded half-up.

Why this case matters

Experience rating multiplies manual premium, so a wrong split, weight or reduction shifts an employer's premium.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
mixed claim history 0	`75`	`88`	Failed

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