Descriptive statistics were used to measure prevalence of demographics and each of the selected illegal behaviors over time within each group (POUD and No POUD). Descriptive statistics were also used to measure prevalence of sources of prescription opioids within the POUD group. To simplify data presentation, demographic and illegal behavior prevalence data were averaged into three multi-year time periods: 2002–2005, 2006–2009, and 2010–2014. Source prevalence data were averaged into two multi-year time periods: 2005–2009 and 2010–2014.
