“I’d like to know “
Stuck in my head from at least 10 years ago, I can try to look up. Note your stat refers to pack a day. The 1 in 6 refers to all smokers, i.e., including those over a pack a day.
Other number that stuck with me it takes 30 “pack years” (1 pack a day for 30 yrs or 2 for 15, etc.) to present irreversable and noticeable pulmonary reduction in later life compared to non smokers, measured in FEV - forced expiratory volume.
“pack a day” means that and any amount greater.
In any case I wish you luck finding a number for that now. My stats come from the ‘80s when government agencies just published the data they collected and collated.
About ten years ago I tried to find such a statistic on the internet searching every medical source of data, gov and private, and after a couple of fruitless hours gave up. It was obvious to me then that real figures on lung cancer rates was no longer being published for public consumption.