A BBC investigation into crimes committed by children aged under 10 has revealed mixed results across Wales.
The age of criminality in Britain is lower than many European countries
In the Dyfed-Powys Police area, recorded crimes almost doubled in the last financial year from 66 to 115.
South Wales Police saw a sharp drop from 86 to 42, and in Gwent, figures reduced from 127 to 70. North Wales Police saw 76 crimes recorded.
If nine or under, a child cannot be charged with an offence in England and Wales, although crimes are recorded.
In Dyfed-Powys, the number of recorded crimes by children under 10 rose from 66 in 2004-2005, to 115 crimes in the last financial year.
In 2006-2007, the force dealt with 23 assaults, three cases of arson and one case of possessing cannabis.
North Wales Police revealed 11 cases of shoplifting, 28 assaults, three cases of arson and 34 cases of criminal damage in the last financial year.
Gwent Police recorded 70 crimes involving under 10s in 2006-2007, compared to 127 incidents in 2004-2005.
South Wales Police followed a similar trend, recording 42 crimes in 2006 - compared to 86 in 2005.
Figures from 32 of the 43 forces across England and Wales show that overall, 2,840 crimes were committed by a child under 10 last year.
Around half were cases of arson or criminal damage. There were also 66 sexual offences, including a number of sexual assaults on children under 13.
The figures were obtained by BBC Radio Five Live through requests under the Freedom of Information Act.
They also reveal that children too young to face charges were suspected of harassment, wounding and burglary.
Children committed 66 sex offences in England and Wales last year
Paul Cavadino, chief executive of the National Association for the Care and Resettlement of Offenders (Nacro), said: "Reducing the age of criminal responsibility would not help to reduce crimes committed by young children.
"The best approach to serious child offenders is to deal with them as children who need effective care measures.
"This country's age of criminal responsibility, at 10 years, is already unusually low by European standards."
He added: "Instead they deal with them in family proceedings courts which can impose compulsory supervision and care measures.
"This is a more sensible approach than processing children through the criminal justice system."
As a proportion of total crime, the number of offences committed by children under 10 is small.
Home Office figures show there were 5.5 million incidents reported to the police during the same period.