Math question, non sports....

[Doug]

If you had a nation that was perhaps an island ( as in isolated) but also highly overpopulated ( like say China) as the background.

The gov't decides that each couple ( or even each woman) can only have two children in her lifetime ( we will allow the rare triplets and such to live). These people live a long life on average, say 90 years. Nobody can move to or from this country, so no immigration +/-.

What happens to the population of this country ?

I think short term it continues to grow, but long term it shrinks. My reason is some females would be lost to accidental death, fertility issues, homosexuality, etc. There should be plenty of males left to impregnate the remaining females, though.

Population has to shrink over centuries, right ?

[ouman101]

There will still be people that have more than 2 kids and then hide them. Also, women who are infertile will want to adopt.

However, I guess if it takes two people (man and women) and they can only have 2 more kids. Technically, this is a 1 to1 relationship and not everyone will have kids. So, you're probably right that in the long run population will decline.

[gryfyn1]

2.1.


That is the live birthrate per woman at which a population stays stable.

Giving a max of 2 (with the odd multiple birth) the birth rate per woman would be significantly lower accounting for childbearing woman who don't have children.

Depending on the current age of the population, the extending of the of the lifespan of the elderly will cause an increase until that number stabilizes. at which point the population will fall.

This is what is happening across Europe and Japan currently.

[Doug]

2.1.


That is the live birthrate per woman at which a population stays stable.

Giving a max of 2 (with the odd multiple birth) the birth rate per woman would be significantly lower accounting for childbearing woman who don't have children.

Depending on the current age of the population, the extending of the of the lifespan of the elderly will cause an increase until that number stabilizes. at which point the population will fall.

This is what is happening across Europe and Japan currently.

That sounds right to me. If the replacements don't come along at that 2.1 / 2.0 clip then the population should decline in a modern nation ( like a Japan) barring disastor. now a primitive African culture might need 6 kids per woman to stay stable, or whatever number.

I thought China put up some limit like 2 kids and continues to grow population. The math didn't work out in my head. A 2/2 ratio should equal a declining population over time....was my instinct.

[Doug]

There will still be people that have more than 2 kids and then hide them. Also, women who are infertile will want to adopt.

However, I guess if it takes two people (man and women) and they can only have 2 more kids. Technically, this is a 1 to1 relationship and not everyone will have kids. So, you're probably right that in the long run population will decline.

Well nice way to bend the question ?

If you want to go way out there....

Abort male babies in China and keep the female ones ( opposite of reality) and you might increase population ?

[gryfyn1]

That sounds right to me. If the replacements don't come along at that 2.1 / 2.0 clip then the population should decline in a modern nation ( like a Japan) barring disastor. now a primitive African culture might need 6 kids per woman to stay stable, or whatever number.

I thought China put up some limit like 2 kids and continues to grow population. The math didn't work out in my head. A 2/2 ratio should equal a declining population over time....was my instinct.

that correct China actually has a negative population growth from live childbirth but the fact that health care has improves vastly, especially in rural areas over the last 40 years means, that alot more people aren't dying causing the average age to go up.

[Salamander]

I have two parents. They each had 2 parents. My 4 grandparents each had 2 parents. Therefore if we go back far enough through the generations, there once were an infinite amount of people on the Earth.

[Doug]

I don't get what what you guys say.

If 50% of children are female, and each can only have 2 kids ( at 50 % female presumably), population should decline over time. Prove this wrong with no immigration gain.

Somebody said 2.1 kids is maintaning a balance...that all depends, but it has to over 2.00 , IMO.

[Doug]

that correct China actually has a negative population growth from live childbirth but the fact that health care has improves vastly, especially in rural areas over the last 40 years means, that alot more people aren't dying causing the average age to go up.

Then when the old Chinese die off and population control kicks in there will be a decrease in the current Chinese population of maybe 1.6 billion in say the year 2060, in theory ?

[Doug]

It seems to me given 50% of the population is female

A birth rate over 2 per female must be obtained to not lose population.

How much over two is debatable....

it might be be 5.5 in Africa or Detroit

or 2.2 in a civilized country.

[benjy]

It seems to me given 50% of the population is female

From Wikipedia's Sex Ratio entry:

"The human sex ratio is of particular interest to anthropologists and demographers. In humans the secondary sex ratio is commonly assumed to be 105 boys to 100 girls (which sometimes is shortened to "a ratio of 105"). In human societies, however, sex ratios at birth or among infants may be considerably skewed by sex-selective abortion. The CIA estimates that the current world wide sex ratio at birth is 107 boys to 100 girls. The value for the entire world population is 101 males to 100 females"

[Cap dat 4ss]

I have two parents. They each had 2 parents. My 4 grandparents each had 2 parents. Therefore if we go back far enough through the generations, there once were an infinite amount of people on the Earth.

search pedigree collapse and get back with us.