Thank you for downloading this week's more or less podcast. Here's Tim Harford.

Hello and welcome to more or less the program that does for dodgy numbers

What the Spanish Inquisition did for religious pluralism?

You didn't expect that did you?

This week we unpicked statistics on disability and on immigration

and we ask what's happening to primary school maths

and we'll try to work out what the world population would be today

if the First World War had never happened.

Not easy. In fact, it's hard even to figure out what the world did to the world's population back then.

One of the paradoxes of the Great War is that the bloodiest, most murderous war in history

produced a totally unexpected and unplanned improvement in the standard of living

and in the life expectancy of the civilian population.

But first, as the nation's school children get used to being back in the classroom

after their long summer break, we've decided to take a closer look

at what they'll be learning there.

Most parents simply wouldn't recognise the way their children are being taught mathematics in primary school

although the current methods were introduced through the national numeracy strategy in 1999.

They're not compulsory but they were recommended and are widely used.

I spoke to Laurie Jacks until recently mathematics coordinator at a primary school

and now an independent mathematics consultant.

Ideally we want all children to have an efficient method of calculating

but at some points along the way children aren't quite ready to move on and just learn a process

...