Coale A J, John A M, Richards T
Demography. 1985 Nov;22(4):611-23.
The mathematics of stable populations recently has been generalized to cover populations with time-varying fertility and mortality by a modification incorporating the sum of age-varying growth rates in place of the fixed growth rate of a stable population. Equations that characterize nonstable populations apply to any cohort-like phenomenon with a measurable property that cumulates gains or losses through time. In particular, the equations fit the relation between a population's average parity at a given age and age-specific fertility rates previously experienced at lower ages. Techniques devised to derive an intercensal life table from single-year age distributions in two censuses are adapted to estimate accurate intercensal fertility schedules from distributions of parity by age of woman in two censuses. Birth-order specific fertility schedules are also estimated.
稳定人口的数学理论最近已得到推广，通过一种修正方法涵盖了生育率和死亡率随时间变化的人口情况，该修正方法纳入了年龄变化增长率的总和，以取代稳定人口的固定增长率。描述非稳定人口的方程适用于任何具有可测量属性的队列式现象，该属性会随时间累积收益或损失。特别地，这些方程适用于特定年龄的人口平均胎次与较低年龄之前经历的年龄别生育率之间的关系。为从两次人口普查的单年年龄分布推导普查间生命表而设计的技术，被用于从两次人口普查中按女性年龄划分的胎次分布来估计准确的普查间生育率时间表。还估计了按出生顺序划分的生育率时间表。
