On More or Less we patiently survey the statistical landscape. It's a kind of mathematical stakeout. When, finally, a number-abuser strays out into the open - we pounce.
Our victims are usually journalists or politicians. But of course now there are other channels open to the purveyor of rogue statistics.
A recent YouTube video, Muslim Demographics, uses data to portray the rapid Islamification of Europe and the United States. The claims it makes are rather startling.
But is a YouTube video fair game for More or Less? It's an interesting question - not least because we don't know who made the video. Or why (though one might speculate).
We decided to pounce. After all, the video's been played over 10 million times. That's a big hit. And it chimes with a thesis - the rise of 'Eurabia' - which has some traction elsewhere.
So how reliable are the statistics in the Muslim Demographics video? The short answer is: not very. But the long answer is more interesting, because the video is mix of the right, the wrong and the unknowable.
It's quite hard to dispute a figure for which there's no firm data either way. Take, for example, the video's claim that half of Dutch new-borns are Muslim. The Dutch cannot provide the relevant data because they don't collect it.
But Dutch statisticians estimate a Muslim population of 5 per cent of the total population. So to put it bluntly: could 5 per cent of Dutch women really be having 50 per cent of Dutch babies?
It sounds unlikely. But it's not an easy question to answer. If you want to see how we set about it, you might like to read this essay by my colleague Oliver Hawkins. Indeed, if you're into maths, we positively encourage you to; you might be able to suggest an even more elegant calculation.
The video is over seven minutes long, covering more ground than we could deal with on the radio. So we've made a video of our own - a more thorough analysis - and we've posted it on YouTube as a reply to the original video. It's embedded here, too.
If you like it, do pass it on.
Richard Knight is Series Editor of More or Less
- You can embed the More or Less video on your own web site: click the 'share' button at bottom right of the video and copy the embed code to your web page.
- The new series of More or Less starts today at 1330 on Radio 4. In the first programme Tim Harford investigates statistics which some claim reveal the 'Islamification' of Europe and checks whether the Home Office has been doing its sums properly. Do its claims about the DNA Database really add up?
- Muslim Demographics on YouTube and the More or Less reply.
- Richard Knight has written a longer piece about Muslim Demographics for the BBC News Magazine.