How Did Benjamin Gompertz Predict Our Deaths?

'A Dance of Death' by Michael Wolgemut (1434–1519), a German painter and printmaker. Historical Picture Archive/Corbis/Getty Images

Having a legacy is nice, but what if the discovery that bears your name in perpetuity is something that predicts the death of every human on the planet? It didn't really seem to bother Benjamin Gompertz much. Gompertz wasn't a fortune teller or the Grim Reaper or anything — he was an actuary, someone who calculates the financial risk an insurance company assumes by insuring people — but the "mortality equation" he formulated in 1825 is still our most useful tool for describing how humans and many other animals die out over time. And what the Gompertz law of mortality tells us is just as chilling today as it was then.

Gompertz was born in London in 1779 to a successful diamond dealer. Though the family was wealthy enough, they were also Jewish, which excluded Benjamin from studying at a university at that time. But boy, did that kid ever love math, so he taught himself, doggedly submitting papers to math publications throughout his early career while working a day job at the London Stock Exchange. But what he really wanted was to be an actuary, a vocation that would allow him to combine his obsessions with math, statistics and financial theory. Unfortunately, nobody would hire Gompertz because of his religion.

In 1824, he quit the stock market after the death of his 10-year-old son and was subsequently hired as an actuary for his brother-in-law's new insurance company. The next year he submitted a paper to the Royal Society entitled "On the nature of the function expressive of the law of human mortality, and on a new mode of determining the value of life contingencies." In it he suggested that for most of our adult lives, our chances of dying increase exponentially as we age. It wasn't good news, but it got people's attention.

Gompertz pretty much nailed the way to calculate age-specific death rates. Of course, he did it to help his insurance company figure out the appropriate rates for buying and selling annuities, but maybe the death of his only son drove him to seek a more comprehensive understanding of the age-related trends behind death. Either way, Gompertz gave us an equation stating that after around age 30, the odds of a person's buying the farm roughly doubles every eight years.

So, assuming you were at least 30 years old eight years ago, you were half as likely to croak then as you are today. Nobody's been able to prove this equation wrong for nearly 200 years, although another British actuary named William Makeham came along about half a century after Gompertz and added a good bit to the original math that calculates risk of death, assuming equal risk for everybody of dying from certain specific dangers, no matter what age we are.

And in case you were wondering, Benjamin Gompertz died at the ripe old age of 86.