Limitations
The two main limitations of the study concern: first, its generalizability to other populations, settings and pack sizes; and secondly, the lack of biochemical measures of nicotine exposure. The study was conducted in Canada where, in the majority of provinces, cigarettes are sold in only two pack sizes—20 and 25. This was an advantage for the current study. There is no reason why smokers in Canada should differ from those elsewhere, but this remains an uncertainty. Participants were broadly representative of smokers in Canada in terms of their age, income and level of education. They were less representative in terms of gender—with women being over‐represented—and in terms of ethnicity—with white groups over‐represented. While there are no a priori reasons why these differences should affect the impact of the intervention, this merits some caution. The further limitation of the study was the absence of biochemical measures of nicotine to assess the extent to which any reduction in cigarettes per day was associated with a reduction in nicotine exposure. While this would have provided some evidence of the extent to which reducing cigarettes per day resulted in compensatory smoking, this was beyond the scope of the current study.