The British Crime Survey (BCS) and police recorded crime statistics are complementary series, and together these two sources provide a more comprehensive picture of household and personal crime than could be obtained from either series alone.
The main purpose of the BCS is to give a count of crime that includes those incidents that are not reported to the police, or not recorded by them. As such, the BCS asks victims whether an incident had been reported to the police, or whether the police came to know about it another way, and is therefore able to estimate reporting rates. Overall, the 2006-07 BCS estimated that more than half of crimes are never reported to the police. Reporting rates are reported at a national level and published annually in the Home Office Statistical Bulletin Crime in England and Wales. See
http://www.homeoffice.gov.uk/rds/pdfs07/hosb1107.pdf
for the latest figures.