If there were 1401 crime reports then it doesn't necessary follow that there were 1401 different criminals committing those "alleged" crimes does it so there were never going to be 1401 people arrested and charged. Some of the "crime" reports were probably not real crimes as such and if you remove the anti social behaviour element then the 161 charges brought from the remaining 100 gives a charge rate of 16%. In order to prosecute someone you have to have evidence or catch them in the act, I think that's the difficulty. Would you want to waste time gathering evidence about a stolen kit-kat when there's a rapist on the loose? No, 'course not so the police actually ask the victim now if they want the cause taking further and in many cases the victim realises there's little chance of finding the culprit so they say no! This allows the police to focus on the more serious cases where they have a chance of getting a result in court! Hence the apparent poor success rate!