Figure 1
From: Trends in prevalence of substance use among Icelandic adolescents, 1995–2006
Annual prevalence of daily smoking during the last 30 days among Icelandic 10th-grade students, 1995–2006. The proportions shown for each year represent responses that have been collapsed into a dichotomized variable (0 = "Nothing or less than daily" and 1 = "Daily").