The overall mortality rate three years after the injury was 16%, or about one in six people, compared to average expected mortality in the general population of 5.9%, according to the study.

Any gains from having more than one offspring at a time might be expected to be like higher infant and maternal mortality rates.

Tweaking an expected return here or a mortality rate there could magically bring both into balance, often without shareholders, policyholders or regulators being any the wiser.