Mortality

In 1825 an English actuary by the name of Benjamin Gompertz made an important discovery. Gompertz's job as an actuary for an insurance company was to calculate the risk of death for people of different ages in order to determine how much to charge for life insurance. (The exact same kinds of calculations are made by actuaries today.) Using data from various parts of England, where he lived, Gompertz discovered that the risk of death increased in a predictable fashion with age. His calculations led him to conclude that the death rate doubled about every ten years between the ages of twenty and sixty, which was the primary age range for people purchasing insurance annuities at that time. The mathematical formula Gompertz used to predict this exponential rise in mortality after age twenty has become known colloquially as the Gompertz equation, and it has remained an integral part of mortality computations conducted by actuaries and demographers ever since the early nineteenth century.

What made Gompertz's discovery so interesting was not just the fact that he devised a formula Figure 2 Survival/Age SOURCE: Author that accurately portrayed the dying-out process of humans, but that he and others believed that the same formula could be used to characterize death rates for other species. In fact, for more than a hundred years following Gompertz's discovery, numerous investigators from a wide range of scientific disciplines speculated that the Gompertz formula described a fundamental principle of death for all living things, a principle that became known as the Universal Law of Mortality. Recently, scientists have used death statistics for such species as humans, mice, and dogs to demonstrate that there is evidence to support the idea that age patterns of death occur in a consistent way across species, despite the fact that there is a wide variation in the observed lifespans of different species. In other words, there is scientific evidence to suggest that Gompertz was right—there appears to be a nearly universal age pattern to the dying out of living things.