text: Despite this, there are still a few things these data can tell us about the numbers and trends in 
  new OCUs. Firstly, despite the downward bias outlined above, it is clear that there are not 
  enough new crime-involved OCUs entering the population to cause this trend to increase or 
  even flatten. Secondly, it is assumed that the probability of arrest stays roughly constant through 
  the period, the trend in the number of new positive testers, who are actually captured from the 
  original cohort, will gradually flatten, whereas the decline in new OCUs in the DIP data is almost 
  linear, suggesting that numbers entering the population are also falling. But most important is 
  that the absolute number of new positive testers in 2013 is only 4,281. Given that this figure is 
  likely to include some individuals who are actually long-standing OCUs, but who have evaded 
  arrest to that point, then the number of genuinely new arrested OCUs in 2013 must be lower 
  than 4,281, possibly markedly lower. 
  
  To investigate this further, the next two tables break down annual totals for all tests and all 
  unique individuals, by the year of first test. 