Lorenz curves
Distribution of the overall consumption among OCS users in 2018 is illustrated in a Lorenz curve (27) in Figure 4 . Lorenz curves for the year 1999 and 2009 are available in the Online Supplement . Overall, we found the top 10% most heavy OCS users accounted for almost 50% of the total OCS consumption, though with a decreasing tendency from 49% in 1999 to 46% in 2018. Correspondingly, we found a decreasing Gini coefficient from 0.60 in 1999 to 0.49 in 2018, confirming a reduced inequality of OCS intake among users.