text: The steadily falling trend in arrests corresponds with the steadily falling trend in acquisitive 
  crime, as measured both by police statistics and the Crime Survey of England and Wales (ONS, 
  2014). The number of DIP tests follows a quite different trend for most of the series. That the 
  two trends differ is to be expected for the following reasons. 
  
  i) 
  
   Around 15 per cent of offences for which DIP tests were given were for non- 
  acquisitive crimes. 
  
  ii) DIP only tests individuals aged 18 and over (and we excluded those aged 60+) 
  
  whereas arrests will include individuals outside this age range. 
  
  iii) Until 2006 DIP testing occurred at the point of charge rather than arrest, and not all 
  arrests result in a charge. The result of this is that the number of DIP tests would be 
  likely to increase markedly from 2004 and 2005 to 2006. 
  
  iv) DIP’s geographical coverage was not 100 per cent, and varied through the series (see 
  
  Appendix). 
  
  With these caveats in mind, it is clear that the increase in total tests (and hence total positive 
  tests) in the early years of the series is almost certainly due primarily to the expansion of DIP 
  (points iii and iv), rather than because of an increase in the actual number of opiate and/or 