So I guess many of you are probably aware that most countries now have sub-replacement fertility. That is, without immigration, their population will decline. This is already happening in Japans, which allows little immigration. Countries such as the United States and the UK will continue to grow in population only if immigration continues.

2.1

That is the average number of children each woman has to have for each generation to replace the last. The extra .1 is to make up for early death. This is really well known and widely reported. But it is wrong! So where does it come from? Well, you see there is a tendency for more boys to be born than girls. Usually, about 105 boys are born for every 100 girls. So, that means that 100 women will have to have 210 babies to ensure that there will be the same 100 women in the next generation.

So what about early deaths? Well, this can vary from country to country. In the US roughly 3% of female births don’t make it to 40. If we assume for simplicity that this 3% doesn’t have offspring, then each woman would 210 / 97 = 2.165.

A significant difference.

But, it becomes truly significant when you look at China. In China, the fertility is about 1.3 children per woman. You’ll read once again incorrectly in newspapers that this is far below the replacement level of 2.1. In China, there has been a practice to abort/kill baby girls. So, instead of 210 boys for every 100 girls, it’s more like 230.

Now I’d imagine life is far harder in China. I could easily see a death rate of 5%

This would give replacement fertility of 230/95 = 2.42.

China has a deficit of 1.12 children per woman.

The world fertility was given as 2.3 a few years ago. The population bomb is now a dud, I reckon if only proper calculations were carried out.

Please let me know what you think of this post and don’t forget to join my mailing list if you have not already done so.