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>1.86 babies, well below the 2.1 needed for a stable population Should it not be 3 babies or over? Maybe my lack of statics knowledge is my problem. But if tw
by dghughes 12y ago
>1.86 babies, well below the 2.1 needed for a stable population
Should it not be 3 babies or over? Maybe my lack of statics knowledge is my problem.
But if two parents have two kids that's zero population growth if they have three kids that means they've replaced themselves plus added one more person to create population growth.
- dsymonds 12y ago"stable" here means zero population growth over the long term, which actually requires a little above 2 per couple to account for people who die before being old enough to parent children. 2.1 is the common approximation for that.
- dghughes 12y agoI see what you mean stable versus growth I just assumed growth was needed to survive not just stability.
- JoeAltmaier 12y agoBut people live after they reproduce. Having 2 children, and every 2 in the next generation have 2 more, etc, means population continues to grow. A steady state is reached, but as lifespan increases so does population. The obvious limit is, if lifespan is infinite, then 0 children is the only number that permits a stable population.
- TylerE 12y agoEventually the older generations die. That stabalizes things.
- baddox 12y agoThe average human lifespan is a relatively fixed sized buffer. Since everyone who is born eventually dies, input matches output, and there's no population increase other than the average lifespan (and thus the buffer size) increasing.
- Dylan16807 12y agoI don't understand your question. Stability and growth are different things. Not all couples need to have extra babies to have growth. Why did you bring up growth?