Gompertz Survival Kinetics: Fall in Number Alive or Growth in Number Dead?

The classical Gompertz assumption that the number of individuals surviving in a population decreases with age at an exponentially increasing rate often fits actual data poorly. In particular, observed mortality rates of the older individuals may be lower than predicted. However, such data can be very well fit by the alternative assumption that the number dying increases at an exponentially decreasing rate. Thus, when the appropriate form of the Gompertz kinetics is used, the older individuals die according to the same rule as the younger.