A lump sum compensation award is not simply a weekly loss figure multiplied by the number of years remaining. Life expectancy determines the period over which future losses are projected, and small differences in that period can produce large differences in the final award.

Two sets of life expectancy data are commonly used in NSW personal injury matters: the ABS life tables and the Cumpston Sarjeant medium life expectancy figures. The difference between them can meaningfully affect the size of a lump sum award.