World’s population has hit 8 billion

The world's population has hit eight billion, just 11 years after passing the seven-billion milestone, the United Nations has said.

After a big surge in the middle of the 20th Century, population growth is already slowing down.

It could take 15 years to reach nine billion and the UN doesn't expect to reach 10 billion until 2080.

It's hard to calculate the number of people in the world accurately, and the UN admits its sums could be out by a year or two.