Gompertz-Makeham Law of Mortality

The Gompertz-Makeham law is the foundational parametric model of adult human mortality. Benjamin Gompertz showed in 1825 that the force of mortality rises exponentially with age, and William Makeham added an age-independent background term in 1860 to account for deaths from causes unrelated to ageing. The combined law expresses the hazard of death as a constant plus an exponentially increasing component, capturing the dominant shape of adult mortality with just three parameters.