It may not be as simple as that. Studies show the dose-response relationship of smoking is not linear where cardiovascular effects are concerned (it is in the case of cancer). From a paper published in Am J Public Health:
So, smoking just a few cigs a day does appreciable damage regardless if you smoke more than that (again talking about cardiovascular health. Cancer is directly related to how much one smokes).
I understand that, otherwise the day after you stopped smoking you'd feel like a million bucks and be 100% healthy, but it doesnt work like that obviously.
That said, if you're trying to argue that smoking 1 cigarette a day is same as smoking 20 a day, im going to to have to disagree.
Every cigarette not smoked is % of harm reduction, imo, thats the nice thing about harm reduction, it doesn't require nice whole numbers, even fractional health gains add up given enough time.
Did y'all hear about this crap this week????)