FA-62990 / Insurance premium rating / Member archive

Square-root credibility rate indication: Zero-claim books are rejected · case 05

A book with no claims returns invalid instead of the complement.

Member previewVariant 5 · 3 implementations · 9 checks per implementation

Case contract

Input claims n, full_standard, observed and complement changes (per mille), cap. n<0 or full<=0 -> 'invalid'. Z (per mille) = min(1000, isqrt(n*10^6 // full)). Indication = floor((Z*obs+(1000-Z)*comp)/1000+1/2), then clamped to [-cap, cap]. Return [Z, indication].

Why this case matters

Credibility weighting decides how far a rate change follows thin experience versus the complement.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
zero claims uses complement	`"invalid"`	`[0, 7]`	Failed

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