What is a life table?
A life table is a statistical table that shows the probability of a person dying at each age. It answers the question: "Given that someone is alive at age 35, what is the probability they will still be alive at age 60?" Actuaries use life tables to value future income streams because you can only earn income while you're alive.
Why Koch?
In South Africa, the standard life tables used in personal injury litigation are those published by Professor Robert Koch. Koch's tables are based on South African population mortality data and are widely accepted by the courts. They are published in The Valuation of Damages and are updated periodically.
The most commonly used version is Koch Table 2, which reflects general population mortality. There are separate tables for males and females, because mortality rates differ by gender. Some actuaries adjust Koch mortality up or down depending on the claimant's health, occupation, or socioeconomic group — this is called a mortality adjustment.
How do they affect the calculation?
Life tables feed into the life annuity factor — the multiplier used to convert a monthly income loss into a single lump sum (present value). A higher mortality risk means a lower annuity factor, which means a smaller capitalised loss. In practical terms:
- A younger claimant has more years of expected future earnings, so a higher annuity factor and a larger claim.
- An older claimant closer to retirement has fewer expected earning years and a smaller factor.
- A female claimant generally has a slightly higher annuity factor than a male of the same age, because women have lower mortality rates on average.
The annuity factor in one sentence
The life annuity factor combines three things: the probability of surviving each future year (Koch table), the time value of money (discount rate), and earnings growth (inflation adjustment). Multiply it by the monthly loss and you get the present value of all future lost income.
For a detailed walkthrough of the full calculation, see How to Calculate Loss of Income in South Africa.
What to watch for
When reviewing an actuarial report, check which life table was used and whether any mortality adjustment was applied. A 10% upward adjustment to mortality (meaning the claimant is assumed to have a 10% higher chance of dying at each age) can reduce the future loss by a meaningful amount. If the opposing actuary has applied a large mortality adjustment, ask them to justify it — it should be supported by medical evidence or occupational risk data.