Playing Politics with Murder

Blog Category: Statistics

The London ‘murder rate’ has become something of a political football as the Mayoral election draws near.

Last year the Evening Standard reported that the number of murders in the capital had fallen to a level not seen since 1978. On Saturday the Times reported that it had continued to fall to a level not seen since 1969.

Boris Johnson is naturally happy to claim that the number of murders has fallen by 25 per cent since he took office in 2008.

Yet Ken Livingstone was also able to point to statistics showing that the number of murders had recently increased by 7.6 per cent. How is this possible?

The answer is that it depends on the period you look at, as there can be wild variations from month to month.

As the Full Fact organisation has pointed out in its analysis of the claims by both Boris and Ken, small variations can lead to large percentage swings.

The Evening Standard article in January 2011 was based on the calendar year – which highlighted a drop to 125 homicides in 2010 from 133 in 2009.

Whereas the Times article was using the Met statistics for the financial year [April to March], giving a total of 103 in 2011/12 compared to 120 in 2010/11. Interestingly, the 2010/11 figure was an increase from 113 in 2009/10.

Then we have the latest stats provided by the MPA for the year November 2010 to October 2011 with an increase of 9 homicides (or 7.6 per cent).

The reason for this disparity seems to lie a cluster of homicides at the end of 2010 and the start of 2011. There were 12 in December 2010, 13 in January 2011 and 15 in February 2011.

By contrast the numbers for the end of 2011 and the start of 2012 remained low – the Met’s rolling tables show eight in December 2011, three in January 2012 and seven in February.

This also explains why there is a massive 24 per cent decrease in the homicides for the 12 months to February 2012 (104) compared to the 12 months up to 2011 (137).

Politics aside, the good news is that there is no denying that the official statistics show the number of homicides has steadily decreased since 2003.

Note: Official statistics are based on the number of homicides, which include manslaughter and infanticide as well as murder. When politicians talk of murders they are really talking about homicides. Likewise, murdermap is really a homicide map.

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