Thank you for downloading the more or less podcast. We are weekly guide to the numbers in the news and in life.

And I'm Tim Halford.

The most important stories are not necessarily the ones that lead the news bulletins.

In the post-war years one of the most significant stories was the

travelling of the world's population. But that rarely made headlines.

We may look back in this century at a different birthrate trend.

Take this feel-good headline from the UK newspaper The Telegraph.

Western civilization is doomed without more children.

The article starts with the cautionary tale of South Korea, the country with the lowest birthrate in the world.

The average South Korean woman can now expect to have 0.78 children in her lifetime.

Well below the 2.1 needed to maintain a stable population.

Now those figures are correct. South Korea has a really low birthrate.

But what caught our collective eye were the figures in the next sentence.

At this rate there will be just six grandchildren for every 100 Koreans today.

This is a really striking claim.

If true. But when we tried to check the numbers we weren't sure it was right.

Luckily we knew the band to ask Rob Eastaway, author of books such as Maths on the back of an envelope.

And as usual he had an envelope to hand.

So let's say we have 100 people then there will be 50 women 50 men let's say so they form 50

couples for the point of view of producing children. And if the fertility rate is 0.78 we

therefore expect those 50 couples to produce 39 children. So that's 39 children to replace the

100 who were in the generation above them. Those children those 39 children let's call them 20

...