Kim Y J, Sykes Z M
Demography. 1978 Nov;15(4):559-69.
We discuss two special cases of population dynamics with changing vital rates subject to the constraint NRR = 1 and consider the specifics of ergodicity and stationarity. By restricting the number of age groups to two, we can make explicit the way weak ergodicity works. When mortality is constant and the period NRR = 1, a life-table stationary population eventually results; everything of demographic interest (except age-specific fertility and the cohort NRR) is asymptotically constant. With changing mortality, but both period and cohort NRR = 1, only weak ergodicity holds, and everything changes over time.
我们讨论了在净再生产率（NRR）= 1的约束下，具有变化生命率的种群动态的两种特殊情况，并考虑了遍历性和平稳性的具体特征。通过将年龄组数量限制为两个，我们可以明确弱遍历性的作用方式。当死亡率恒定且时期净再生产率（NRR）= 1时，最终会形成一个生命表稳定种群；所有人口统计学感兴趣的指标（年龄别生育率和队列净再生产率除外）渐近恒定。在死亡率变化，但时期和队列净再生产率均为1的情况下，仅存在弱遍历性，且所有指标都会随时间变化。
