The shifted Hadwiger fertility function

Abstract The age-specific (female) fertility rates ƒ(y) are usually defined by applying the conventional definition of the birth rate to the sub-population consisting of y-aged females. Without further notification only live-born girls are taken into account; in the cases where both live-born girls and boys are considered the rates may be indicated as “total”. We distinguish between the above “gross” rates and the “net” rates p(y)ƒ(y), where p(y) refers to the probability that a new-born girl will be alive at age y. Apart from proportionality factors these interdependent rates often show only small differences in a given situation.