The global fertility rate is declining. This means that the average number of children a woman gives birth to is falling. And as a result, nearly every country could have shrinking populations by the end of the century.

And 23 nations – including Spain and Japan – are expected to see their populations halve by 2100.

Researchers at the University of Washington’s Institute for Health Metrics and Evaluation showed the global fertility rate nearly halved to 2.4 in 2017 – and their study, published in the Lancet, projects it will fall below 1.7 by 2100.

If the number falls below approximately 2.1, then the size of the population starts to fall.

As such, the researchers expect the number of people on the planet to peak at 9.7 billion around 2064, and then fall down to 8.8 billion by the end of the century.

So what’s causing this drastic fall in fertility rates? Well, it has nothing to do with sperm counts or the usual things that come to mind when discussing fertility. Instead, it’s because more women are choosing not to have children. More women are pursuing education and work, and they now have greater access to contraception, leading to women choosing to have fewer children.