Harsh sentences given to the rioters of 2011 appear to have acted as a deterrent, a new analysis reveals. But it also shows that, while "riot crimes" such as burglaries, criminal damage and violence against the person dropped immediately afterwards, there was a spike in other offences.

The findings will be studied closely by politicians, sociologists and judges as they seek to learn the lessons from the riots during which more than 5,000 crimes were committed.

In the 88 areas hit by rioting in London, crime rose by 57% during August, the month of the riots, according to the analysis by Laura Jaitman and Stephen Machin at University College London and Brian Bell at the University of Oxford, published in this month's Economic Journal.

A year after the riots,some 4,600 people had been arrested and 2,250 appeared in court. The research shows that rioters who ended up in court were almost three times more likely to be placed in immediate custody than people who had committed the same type of offences the previous year. "For all crimes, the immediate custody rate tripled from 12% to 36% in magistrates' courts and rose from 33% to 81% in crown courts," the authors note.

Sentences were on average approximately two months more than the 13 months received by similar offenders the previous year. The tougher sentencing appears to have sent clear signals across the capital. There was a decline in "riot crimes" even in Londonareas far from the riots. The economists believe this was becauseprospective criminals feared the tougher sentencing regime had become a permanent fixture. However, over the following six months there was a rise in other crimes such as drugs offences, fraud and forgery.

"This suggests a rational response from criminals who seem to have substituted away from the types of crimes that received tougher sentences to those that did not," the economists conclude.