text: Comparing 2004 with 2013 shows that the younger age groups have seen falls in both the 
  number and the proportion of new positive testers. However, the proportion of those aged 40+ 
  has consistently risen and now constitutes the largest group of all new individuals testing 
  positive. 
  
  This means that the 4,281 individuals testing positive for the first time in 2013 has a very 
  different age profile to that we would expect from a cohort of recent initiates. It is far older, 
  suggesting again that many of those are actually pre-existing users only tested (positively) for 
  the first time in 2013. This adds further weight to the back-of-the-envelope modelling evidence 
  demonstrating that a substantial proportion of the 4,281 new positive testers in 2013 are likely to 
  be longer-term users who have only been first arrested in 2013, rather than genuinely new 
  OCUs. 
  
  In the next section, analysis will examine whether there has been a possible shift towards an 
  older profile amongst new initiates. But even taking this into account, it is unlikely that the 
  majority of those 4,281 individuals are recent initiates. This can be seen clearly in Figure 8 
  below, which compares the age-of-initiation curve from Figure 11 (in the next section) to the 
  2013 ‘new-individuals’ cohort in the DIP data. 