FA-63598 / Actuarial life tables / Member archive

Central death rate to mortality rate conversion: Constant-force conversion returns survival · case 03

Low mortality groups get q close to one.

Member previewVariant 3 · 3 implementations · 10 checks per implementation

Case contract

Input deaths, exposure [num, den] central person-years, method udd|cfm|actuarial. m = deaths/exposure. UDD q=m/(1+m/2); constant force q=1-exp(-m); actuarial q=deaths/(exposure+deaths). exposure<=0 or deaths<0 -> 'invalid'; q>1 -> 'rate exceeds unity'; other method -> 'unknown method'. Return [m, q] rounded to 8.

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
cfm typical	`[0.0374415, 0.96325077]`	`[0.0374415, 0.03674923]`	Failed

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