This is the short edition of More or Less.

First broadcast on the BBC World Service.

Thank you for downloading from the BBC.

The details of our complete range of podcasts and our terms of use

go to BBCWorldService.com slash podcasts.

Hello and welcome to More or Less on the BBC World Service.

I'm Tim Harford.

In today's programme, a statistician tries to plan a wedding.

But first, how much does immigration cost or benefit a country's economy?

Ruth Alexander has been looking at this.

Yes, and as I don't need to explain to an economy nerd like you, Tim,

the standard measure of the size of an economy is GDP,

which stands for gross domestic product.

But that can't be the right measure here,

because of course the more people you have in a country,

the larger its GDP will be.

The new people will have jobs, they'll need feeding,

they'll be spending money in shops.

The question most people would want answered is,

how does GDP increase above and beyond that effect?

So yes, and the trick is to divide GDP

by the number of people living in the country.

...