On Thursday Police Minister Nathi Mthethwa presented the SAPS 2012/2013 national crime statistics. In his statement he listed the increases or decreases of various categories of crime in terms, not in absolute numbers, but in the rate or ratio per 100 000 of the population.
Thus he stated, for instance, that total sexual offences decreased by 0.4% and robbery in non-residential premises by 0.6%. He added that there had been an increase of 1.2% in aggravated robbery, 3.3% in residential burglary, 0.6% in commercial crime, and 3.6% in residential robberies.Mthethwa also stated that "we have witnessed a slight increase of 0.6%" in the murder rate.
In absolute terms however there were 16 259 murders in 2012/2013, 620 up from the 15 609 recorded in 2011/2012. This is a 4.2% increase. How then can the differential between a 0.6% increase in the murder rate be reconciled with this 4.2% increase in the total number of murders?
The short answer is, it can't.
One possible explanation is that the population of South Africa grew by 3.3% between 2011 and 2012. However, Statistics South Africa estimates that the population of South Africa only grew by 1.34% between 2011 and 2012 (see here.)
In fact, what seems to have happened is the following: The 2011/2012 crime statistics' ratios per 100,000 of the population were calculated using Stats SA's 2011 mid-year population estimate of 50 586 757. For the 2012/2013 crime statistics the SAPS worked out the ratios using the Stats SA estimate of a population of 52 274 945 in 2012. It then worked out the change in the ratios per 100 000 of the population between the two.