text: cocaine. From this information it is possible to create a distribution, for all presentations, of the 
  lag-time between initiation and their first presentation at treatment. This might show – for 
  example – that only ten per cent of all individuals presenting to treatment do so in the first year 
  of use, but that 25 per cent present within two years, and so on. This means that for each year, 
  we can estimate the number of individuals who have begun an opiate-crack career but who 
  have yet to come to treatment. Adding these to the numbers who began in that year and have 
  come to treatment gives our total incidence estimate for each year. 
  
  The first model uses NDTMS data for the cohort starting use in 2005 (n=8,960), the lag-time 
  distribution for those initiating use in 2005 and presenting to treatment between 2005 and 
  201418 is shown below. 