What proportion of the new jobs created since 1997 have gone to foreign workers?
That is a question which the government has found difficult to answer.
The Department of Work and Pensions had to revise its answer three times in one week: first it said the proportion was 30%, then said it was 41%. The latest estimate is over half.
Why did the government get the figures wrong?
Simple failure to add up everyone in the relevant categories and the use of projections to predict the future were part of the cause.
Presenter Tim Harford spoke to Frank Field MP who spotted the errors using a combination of guesswork, common sense and basic maths.
He found out from Mr Field how he arrived at his figures and asks him whether it really matters that so many foreign workers have taken up jobs in Britain.
Our survey reveals...
"A survey reveals ... 22% of women know they're marrying the wrong man on their wedding day ..., eight out of 10 children say their parents' choices of Christmas presents are a waste of money ... almost six in 10 women have had a secret affair with a colleague."
Numbers sell and numbers tell a story. But is the story always true?
Many of the surveys you read about have been commissioned by a company which wants to get its product in the newspapers and on the airwaves.
The numbers the surveys "reveal" give the company a reason to be talking about the issue at hand and, in the language of the marketing companies, to "own" that issue.
Is it a bit of fun? Or getting in the way of real information?
More or Less went behind the scenes at a large broadcast communications agency which helps clients to design surveys and then pushes the resulting story to the media.
How are the surveys constructed, who is answering them and how do they end up in the headlines?
Our reporter Ruth Alexander spoke to psychologist Dr Petra Boynton from University College London who argues consumer surveys are damaging serious research, and confusing people in the process.
Ruth also spoke to academics who have been hired by public relations companies. Are they making a joke out of science, or spreading understanding to the masses?
A crisis for the kilo?
How much does a kilogram weigh? The guardians of the world's weights and measures are no longer sure.
The reason for this strange phenomenon is bound up in a flaw identified by metrologists - the scientists who set the base units of measurement such as the metre, kilogram, ampere and volt.
Will the way in which we measure the mass of objects change?
These units were originally based on actual objects. In the case of the kilogram, the original prototype was minted from platinum and iridium in the 19th Century. It is stored in a vault in Paris.
But over the years, the original prototype kilogram - when compared to copies stored around the world - seems to have changed mass. It renders all measurements of mass as potentially flawed, and has led to a worldwide search for a new way to define the kilogram.
British scientists are playing a key role, and next week in Paris the world metrology community will meet to thrash the issue out.
On the eve of this global summit, presenter Tim Harford visited the National Physical Laboratory in Teddington, Middlesex to explore the problems - and solutions - to the shifting mass of the kilogram.
Presenter: Tim Harford
Producer: Innes Bowen
BBC Radio 4's More or Less was broadcast on Monday, 5 November, 2007 at 1630 GMT.
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