Ministers in the Coalition Government need to watch their claims more carefully.
 
In the wake of Iain Duncan-Smith claiming the authority of the Office for National Statistics for housing data that came from findaproperty.com, Justice Minister Nick Herbert lent his name to some dodgy claims data on the number of young offenders saved from a life of crime by a new approach.
 
Visiting the Heron Unit at Feltham Young Offenders’ Institution last Thursday in the company of Boris Johnson, the London Mayor, Mr Herbert said that the unit had a reoffending rate of 14 per cent – “much lower than the average” – and showed what could be achieved.
 
Figures from the Mayor’s office amplified the claim, suggesting that the 14 per cent achieved at the Heron Unit should be compared with a national rate of 78 per cent. The claims were reported by The Standard and on local TV news.
 
There are at least two things that can be challenged here. Are they comparing like with like? And how was the 14 per cent reoffending rate claimed for the Heron Unit actually measured?
 
National rates for reoffending among 15-17 year-olds, the group targeted by the Heron Unit, are nothing like 78 per cent. The most recent data from the Ministry of Justice shows that for males it is around 40 per cent. But the unit deals with those given a custodial sentence, where reoffending is much more common, so the 78 per cent figure quoted appears to be about right.
 
The figure is measured by tracking all offences committed by offenders in the year after their release. But to ensure that the great majority of cases are included, the figures are compiled after a six-month wait to allow cases to go through the courts.
 
The Heron Unit has only been open for a year, so the figures cannot be directly comparable. It may be that it has achieved lower reoffending rates: but at present we simply do not know.
 
Second, the sample is quite different. The Heron Unit is targeted at young offenders “who are most motivated to change” the Greater London Authority says. So the boys selected for it are not typical of young offenders generally, but a hand-picked group that those who run the unit believe are most likely to be persuaded to go straight.
 
Nothing wrong with that: but to compare their reoffending rates against a national average is hardly comparing like with like. The MoJ data show that reoffending rates for young people differ widely depending on how many previous convictions they have – those with ten or more previous offences are twice as likely to reoffend as those with one or two.
 
So without knowing the precise characteristics of the Heron Unit offenders, any comparisons are risky. They are more likely to be those with fewer offences, so their expected reoffending rate would be lower anyway.
 
The unit doubtless does excellent work for the minority of Feltham inmates it looks after, and the Mayor may be right to extend its methods – including the provision of “Resettlement Brokers” to a wider range of young offenders – across London. But the statistics hardly prove the case.