Previous studies in Thailand (13), India (14), Germany (in middle age) (15) and Indonesia (16) have shown that smoking is more frequent in low socioeconomic status or low-income groups. Even smoking cessation treatments were less used in groups with low socioeconomic status (15,17,18). World Health Survey data from 48 low-and middle-income countries demonstrated that, in many countries, smoking is more common in low-income groups among males. Among females, it was both prorich (in 20 countries) and pro-poor (in 9 countries) (6). A limited number of studies also determined the causes of inequality in smoking (19)(20)(21)(22), mostly using the decomposition of concentration index. As far as we know, there has been no study or comparison of this issue in the