FA-63370 / Actuarial life tables / Member archive

Life table person-years and expectation: Person-years start from the wrong survivor count · case 05

Life expectancies are overstated by about one year.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Input l (survivors by age, last entry is the open interval) and m_open (per mille central rate of the open interval, <=0 -> 'invalid open rate'). L_x = l_{x+1} + d_x/2, L_open = l_open/m, T_x = sum of L from x, e_x = T_x/l_x rounded to 4 places (None where l_x=0).

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
table 0	`[10.6308, 9.6807, 8.7362, 7.7929, 6.8483, 5.9021, 4.9537, 4.0]`	`[10.569, 9.624, 8.686, 7.7501, 6.8139, 5.8774, 4.9405, 4.0]`	Failed

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