WHAT is the best way to stop teenagers from committing crimes? Some politicians think it is harsher punishment for young offenders. This theory was put to the test in 2010, when Denmark lowered the age of criminal responsibility from 15 to 14, meaning that 14-year-olds now face the criminal-justice system rather than social services. A new working paper finds that after controlling for the long-term decline in crime and seasonality (teenage crime rates tend to fall in the summer as more go off on holiday), 14-year-old Danes were no less likely to make mischief after the change to the penal code than they were before.

The paper's authors, Anna Piil Damm, Helena Skyt Nielsen and Marianne Simonsen, of Aarhus University, and Britt Ostergaard Larsen of the Danish Centre for Applied Social Science, find that the change might actually have had an adverse effect on those 14-year-olds who did go on to commit crimes. Having gone through the criminal-justice system, these youngsters were actually more likely to reoffend between 12 and 18 months after the initial offense than 14-year-olds who committed offences before the reform was enacted. They also did worse in school.

A criminal record hurts job prospects, and raises the odds of recidivism. Prosecutors and the police also treat people with a rap sheet less leniently. Earlier sentencing means that more young people risk falling into this vicious cycle.