  Gompertz's law tells us that for humans above the age of 35 the death rate
increases exponentially with a doubling time of about 10 years. Here, we show
that the same law continues to hold even for ages over 100. Beyond 106 there is
so far no statistical evidence available because the number of survivors is too
small even in the largest nations. However assuming that Gompertz's law
continues to hold beyond 106, we conclude that the mortality rate becomes equal
to 1 at age 120 (meaning that there are 1,000 deaths in a population of one
thousand). In other words, the upper bound of human life is near 120. The
existence of this fixed-point has interesting implications. It allows us to
predict the form of the relationship between death rates at age 35 and the
doubling time of Gompertz's law. In order to test this prediction, we first
carry out a transversal analysis for a sample of countries comprising both
industrialized and developing nations. As further confirmation, we also develop
a longitudinal analysis using historical data over a time period of almost two
centuries. Another prediction arising from this fixed-point model, is that,
above a given population threshold, the lifespan of the oldest person is
independent of the size of her national community. This prediction is supported
by available empirical evidence.
