# The Built-In Human Expiration Date

In the book of Genesis it notes that the human lifespan is limited to a maximum of 120 years. And since God is a mathematician, it shouldn’t be surprising that this rate of mortality is an exponential function:

What do you think are the odds that you will die during the next year?  Try to put a number to it — 1 in 100?  1 in 10,000?  Whatever it is, it will be twice as large 8 years from now.

This startling fact was first noticed by the British actuary Benjamin Gompertz in 1825 and is now called the “Gompertz Law of human mortality.”  Your probability of dying during a given year doubles every 8 years.  For me, a 25-year-old American, the probability of dying during the next year is a fairly miniscule 0.03% — about 1 in 3,000.  When I’m 33 it will be about 1 in 1,500, when I’m 42 it will be about 1 in 750, and so on.  By the time I reach age 100 (and I do plan on it) the probability of living to 101 will only be about 50%.  This is seriously fast growth — my mortality rate is increasing exponentially with age.

As the fascinating article notes, the Gompertz law holds across a large number of countries, time periods, and even different species: “While the actual average lifespan changes quite a bit from country to country and from animal to animal, the same general rule that ‘your probability of dying doubles every X years’ holds true.”