text: The mode age of initiation has shifted from around 18 to around 25 and there is an older age 
  profile throughout. Rises in average age of initiation have also been reported recently in cohorts 
  of Australian injecting drug users (Horyniak et al., 2015). There appear to be two possible 
  explanations. 
  
   There is a genuine shift towards new initiates being older, and for them to present to 
  
  treatment much faster than in previous years. 
  
   There is a consistent, but small number of individuals who mis-report their age of onset 
  
  when attending treatment i.e. who report that they have only been using opiates/crack for 
  a short period when in fact they have been using for a far longer period, and that this is 
  starting to really bias the numbers for recent cohorts because attendees from the original 
  epidemic are becoming smaller. 
  
  It is possible then that the flattening we observe in the incidence trend is due to a small in-flux of 
  older initiates, although mis-reporting may also explain that phenomenon. Either way though, as 
  this analysis has made clear throughout, absolute numbers of new OCUs appear to be small – 
  probably fewer than 10,000 per annum and the numbers of those involved with crime will be 
  smaller still. In addition, despite a flattening in the probable trend in new users, there is currently 
  no sign that it is likely to tip upwards. If anything, the data suggest the downward trend is set to 
  resume, though clearly it remains important to monitor the situation. 