FA-63019 / Insurance premium rating / Member archive

Parallelogram on-level factor: Current-year change area is not triangular · case 04

Changes within the calendar year are credited with too much earned exposure.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Input changes [[month offset from calendar-year start, change per mille]] in order. Annual policies written uniformly; the share of calendar-year earned exposure written after offset d=m/12 is (1-d)^2/2 for 0<=d<1, 1-(1+d)^2/2 for -1<d<0, 0 for d>=1 and 1 for d<=-1. Levels are cumulative products. OLF = current level / earned-weighted average level, returned *1000 rounded half-up.

Why this case matters

On-level factors restate historical earned premium at current rates before comparing to losses.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
single mid-year change	`1025`	`1061`	Failed

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