This might help explain. Below is a section of the following article.
Increase in Deaths in Canada Due to Smoking
Current trends in smoking attributable mortality continue to reflect the smoking behaviour of the population two to three decades earlier. The effect of the drop in tobacco consumption among men, beginning in the mid-1960s, is reflected by the levelling off in the mid-1980s and then continuous decline in male lung cancer rates. In contrast, female smoking rates peaked in the late 1970s and declined slightly in the past three decades. As a result, female lung cancer mortality rates more than quadrupled between 1969 to 1998 and can be expected to rise for the next few years before seeing an expected decrease.
