Concept of Stationary Population in Demography.

#1
The definition of stationary population is:

"The stationary population is a model without immigration or emigration in which the same age-specific probabilities of death apply continuously and in which there are the same number of births and deaths each year."

Can anyone please explain me what does it mean by "the same age-specific probabilities of death apply continuously" in the definition?
 

Dason

Ambassador to the humans
#2
There can be different probabilities for death in a given year for different age groups but these probabilities don't change over time. So the probability a 28 year old will die in the next year is the same year to year. It's a bit more complex than that but that's the gist of it.
 
#3
There can be different probabilities for death in a given year for different age groups but these probabilities don't change over time. So the probability a 28 year old will die in the next year is the same year to year. It's a bit more complex than that but that's the gist of it.
Thank you so much for making it clear to me.

In real life, is it usual to have same age-specific probabilities of death over time? I suppose so. Because if no war or epidemic happens, then the age-specific probabilities of death can be same year to year. Am I wrong? Is the assumption of same age-specific probabilities of death not the real scenario? Is stationary population concept completely theoretical? If it is hypothetical, then why have demographers developed the concept of stationary population? What is the advantage of stationary population? What do demographers establish by considering stationary population?
 
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Miner

TS Contributor
#5
I would include national level medical policy changes in those assumptions. Policy changes such as the smallpox vaccination program in the 60s can have a significant impact on mortality rates.
 

noetsi

Fortran must die
#6
Actually I doubt that the probability of dying at a given age is the same over time in an advanced society. People live longer now than they did in say 1950 because of medical advances nutritional change etc.

It is possible that people can only live so long genetically. Once you reached that limit then there would be stability from then on in these numbers. But I doubt we have reached that point yet.