In response to a request from “Paul in Nottinghamshire”, the BBC’s More or Less has been looking into the claim by the UK government that there are 7 million illegal filesharers in the country.

The widely reported figure turns out to have a rather convoluted back story. The government got it from an advisory body specialising in intellectual property, which got it from a report done for them by a team of academics at University College London, who attributed it to a study by Forrester.

But the BBC’s Oliver Hawkins discovered that it actually came from a different study by Forrester subsidiary Jupiter Research, which was commissioned privately by none other than the British Phonographic Industry, which spends much of its time lobbying for the government to clamp down on filesharing.

Delving deeper into the research behind the claim, they discovered that 7 million was actually a rounding up from 6.7 million, and that that figure was based on 11.6% of a sample of 1,176 households in a survey who admitted to using filesharing. The percentage was hiked up to 16.3% to account for people lying about their dodgy behaviour, and this was then applied to an estimate of 40 million people using the internet – which is in itself significantly higher than the 33.9 million figure that the government would have got from its own source of stats on such things, the Central Office of Information.

Change the population estimate and remove the adjustment for people misreporting their behaviour, and you might come up with a figure of 5.6 million illegal filesharers, or just 3.9 million.

None of this means that the 7 million figure is “wrong”, but the government seems to have been very quick to accept a number that was rounded generously upwards, was based on evidence that it clearly hadn’t checked very thoroughly, was calculated from an estimate of the total population that contradicted its own figures, and was originally commissioned by a partisan body.

Hawkins said: “The number of offenders varies enormously depending on the assumptions you make about consumer behaviour and about the size of the online population.” In this case, the government has swallowed the somebody else’s assumptions (somebody with a vested interest), without asking any questions. And it’s not the first time that a body representing media owners has been accused of overstating the scale of online piracy.

The government can argue that its estimate remains valid. But it might take more than that to win back the trust of Paul in Nottinghamshire.

NB More or Less has its own section on the BBC site, which I highly recommend for anyone interested in the use and abuse of numbers.