Except that, again, you stop before the actual important part starts. In your example, you stop by the 4th generation when you're still in rising period because the mortality hasn't caught up yet.

Here's another example, but going much longer. Here's an example, going up to Gen 8:

Assumptions (to simplify):

• Women have all 1.5 children. I'll round up the number if it's a decimal, just to be nice and to prove my point further (so if we have 5 women, normally it would give 7.5 babies, but we will count as 8).
• No "no-family relations"
• Generation X will make children for Generation X + 1
• Generation X will die at Generation X + 4.

Here's are the details:

Generation 1: 100 new people (50 men, 50 women).

Generation 2: 1.5 * 50 babies are born = 75, bringing the population to 175. Out of those 75 new people, 37.5 are women (rounded up to 38).

Generation 3: 1.5 * 38 babies are born = 57, bringing the population to 232. Out of those 57 new people, 28.5 are women (rounded up to 29).

Generation 4: 1.5 * 29 babies are born = 43.5 (rounded up to 44), bringing the population to 276. Out of those 44 new people, 22 are women.

Now, so far, we agree the population is increasing steadily, and better than if the quality of life were poor and parents kept dying after having children. However, the following is the part you're missing:

Generation 5: 1.5 * 22 babies are born = 33, however Generation 1 is now completely dead (100 people), bringing the population to 276 + 33 - 100 = 209. Out of those 33 new people, 17 are women.

Generation 6: 1.5 * 17 babies are born = 26, however Generation 2 is now completely dead (75 people), bringing the population to 160. Out of those 26 new people, 13 are women.

Generation 7: 1.5 * 13 babies are born = 20, however Generation 3 is now completely dead (57 people), bringin the population to 123. Out of those 20 new people, 10 are women.

Generation 8: 1.5 * 10 babies are born = 15, however Generation 4 is now completely dead (44 people), bringing the population to 94. Out of those 15 people, 8 are women.

Do you start to see the pattern and the problem, now? Arriving at generation 8, you now have way less people than what you started with, and the problem keep getting worse and worse, cause you have fewer and fewer women.

With 1.5 natality, you can expect this community to completely collapse by Generation 15, where you're not even guarentee to have a new woman at all to continue the legacy.

If you lower the natality to 1 (what South Korea has), you get a complete eradication by generation 10.

Feel free to do the calculations with a fertility of 2, and you'll see, it magically equalise everything, because you guarentee 2 individuals will replace 2 dying parents (doesn't matter if they die in 5 years or in 100 years, they will die eventually, and needs to be replaced).

We know your example is flawed, because if you remove immigration from developed countries, they are all losing population, little by little, and not increasing like you claim. And now I've proved it mathematically as well.

Except that, again, you stop before the actual important part starts. In your example, you stop by the 4th generation when you're still in rising period because the mortality hasn't caught up yet.

Here's another example, but going much longer. Here's an example, going up to Gen 8:

Assumptions (to simplify):

• Women have all 1.5 children. I'll round up the number if it's a decimal, just to be nice and to prove my point further (so if we have 5 women, normally it would give 7.5 babies, but we will count as 8).
• No "no-family relations"
• Generation X will make children for Generation X + 1
• Generation X will die at Generation X + 4.

Here's are the details:

Generation 1: 100 new people (50 men, 50 women).

Generation 2: 1.5 * 50 babies are born = 75, bringing the population to 175. Out of those 75 new people, 37.5 are women (rounded up to 38).

Generation 3: 1.5 * 38 babies are born = 57, bringing the population to 232. Out of those 57 new people, 28.5 are women (rounded up to 29).

Generation 4: 1.5 * 29 babies are born = 43.5 (rounded up to 44), bringing the population to 276. Out of those 44 new people, 22 are women.

Now, so far, we agree the population is increasing steadily, and better than if the quality of life were poor and parents kept dying after having children. However, the following is the part you're missing:

Generation 5: 1.5 * 22 babies are born = 33, however Generation 1 is now completely dead (100 people), bringing the population to 276 + 33 - 100 = 209. Out of those 33 new people, 17 are women.

Generation 6: 1.5 * 17 babies are born = 26, however Generation 2 is now completely dead (75 people), bringing the population to 160. Out of those 26 new people, 13 are women.

Generation 7: 1.5 * 13 babies are born = 20, however Generation 3 is now completely dead (57 people), bringin the population to 123. Out of those 20 new people, 10 are women.

Generation 8: 1.5 * 10 babies are born = 15, however Generation 4 is now completely dead (44 people), bringing the population to 94. Out of those 15 people, 8 are women.

Do you start to see the pattern and the problem, now? Arriving at generation 8, you now have way less people than what you started with, and the problem keep getting worse and worse, cause you have fewer and fewer women.

With 1.5 natality, you can expect this community to completely collapse by Generation 15, where you're not even guarentee to have a new woman at all to continue the legacy.

If you lower the natality to 1 (what South Korea has), you get a complete eradication by generation 10.

We know your example is flawed, because if you remove immigration from developed countries, they are all losing population, little by little, and not increasing like you claim. And now I've proved it mathematically as well.

Except that, again, you stop before the actual important part starts. In your example, you stop by the 4th generation when you're still in rising period because the mortality hasn't caught up yet.

Here's another example, but going much longer. Here's an example, going up to Gen 8:

Assumptions (to simplify):

• Women have all 1.5 children. I'll round up the number if it's a decimal, just to be nice and to prove my point further (so if we have 5 women, normally it would give 7.5 babies, but we will count as 8).
• No "no-family relations"
• Generation X will make children for Generation X + 1
• Generation X will die at Generation X + 4.

Here's are the details:

Generation 1: 100 new people (50 men, 50 women).

Generation 2: 1.5 * 50 babies are born = 75, bringing the population to 175. Out of those 75 new people, 37.5 are women (rounded up to 38).

Generation 3: 1.5 * 38 babies are born = 57, bringing the population to 232. Out of those 57 new people, 28.5 are women (rounded up to 29).

Generation 4: 1.5 * 29 babies are born = 43.5 (rounded up to 44), bringing the population to 276. Out of those 44 new people, 22 are women.

Now, so far, we agree the population is increasing steadily, and better than if the quality of life were poor and parents kept dying after having children. However, the following is the part you're missing:

Generation 5: 1.5 * 22 babies are born = 33, however Generation 1 is now completely dead (100 people), bringing the population to 276 + 33 - 100 = 209. Out of those 33 new people, 17 are women.

Generation 6: 1.5 * 17 babies are born = 26, however Generation 2 is now completely dead (75 people), bringing the population to 160. Out of those 26 new people, 13 are women.

Generation 7: 1.5 * 13 babies are born = 20, however Generation 3 is now completely dead (57 people), bringin the population to 123. Out of those 20 new people, 10 are women.

Generation 8: 1.5 * 10 babies are born = 15, however Generation 4 is now completely dead (44 people), bringing the population to 94. Out of those 15 people, 8 are women.

Do you start to see the pattern and the problem, now? Arriving at generation 8, you now have way less people than what you started with, and the problem keep getting worse and worse, cause you have fewer and fewer women.

With 1.5 natality, you can expect this community to completely collapse by Generation 15, where you're not even guarentee to have a new woman at all to continue the legacy.

If you lower the natality to 1 (what South Korea has), you get a complete eradication by generation 10.

We know your example is flawed, because if you remove immigration from developed countries, they are all losing population, little by little, and not increasing like you claim. And now I've proved it mathematically as well.