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A new way of measuring crime in England and Wales has been devised that ranks offences according to their seriousness.

The Crime Severity Score is designed to reflect the relative harm of offending, rather than how many crimes there are.

Under the new system, murder is given the top weighting - 7,979 points per offence - while cannabis possession has the lowest of three points per offence.

West Yorkshire had the highest crime severity score, Dyfed-Powys the lowest.

The Metropolitan Police's score was second highest.

The Office for National Statistics compiled the new system, and said over the past 14 years the police recorded crime rate and the Crime Severity Score (CSS) have shown similar trends - both have generally decreased but in recent years showed slight increases.

Drugs and damage

However, the ONS says the value of the CSS is in providing additional information to understand crime at a local level - although like other police figures, the CSS may fluctuate according to changes in the way forces record offences.

The weighting for each offence is calculated by analysing sentencing data - the tougher the sentence imposed for a particular crime; the greater the weight for that offence.

Once a weight has been calculated for each offence, it is multiplied by the number of incidents.

That total is then divided by the population for the area in question to give the Crime Severity Score.

In England and Wales, the CSS in 2015-16 was 10.1, compared with 14.3 in 2002-03.

After murder and other homicide offences, the next highest individual crime weightings are for attempted murder, aiding suicide, and rape.

The lowest weighted offences after possession of cannabis were soliciting for prostitution, possession of controlled drugs more generally, criminal damage to buildings, and dishonest use of electricity.

'Blunt instrument'

The law and order debate has been hampered for many years by the absence of statistics that reflect the reality of offending.

The police recorded figures are a blunt instrument: they measure only the volume of crimes reported and logged by forces - a murder and a theft each count as one crime, for example.

The other long-standing crime measurement tool is the Crime Survey of England and Wales, the main benefit of which is that it includes offences that aren't reported to police.

But the survey has its limitations as well - some categories of crime are not measured and when it estimates the number of crimes no distinction is made between offences which cause severe harm and those that are less serious.