FA-63548 / Actuarial life tables / Member archive

Joint-life and last-survivor status: Joint status uses the weaker life only · case 03

Joint-life survival is overstated.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Input lx, ly (independent lives, survival zero beyond each table), status joint|last (else 'unknown status'), t. Joint: tp_x*tp_y; last survivor: tp_x+tp_y-tp_x*tp_y. Return [status survival at t, curtate expectation = sum over k from 1 to the longer table length - 1], rounded to 6.

Why this case matters

Life-table arithmetic compounds across ages, so one misplaced index or assumption shifts every downstream value.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
joint life	`[0.9942, 5.8448]`	`[0.992023, 5.77901]`	Failed

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