Surveys. I’ve touched on the usual suspects upholding their own data as though it was the Holy Grail before. ASH is utterly remorseless when it comes to trumpeting their own data, usually for their own means, and they also heap scorn on data that contradicts their sacrosanct view of the populace. Typically, in the UK we have two primary sets of survey data on smoking – the ASH survey (hosted by YouGov) and of course the Smoking Toolkit Study.
Both of these, along with many others run by Cancer Research UK, consistently show that never-smoking-teens rarely pick up e-cigs. They also consistently show little or no progression from e-cigs to combustible tobacco. They also consistently show a decrease in smoking prevalence at the same time there’s an increase in e-cig prevalence. It’s hardly the silver bullet to prove (or disprove) “gateway” theories correct or otherwise; after all it is still perfectly feasible that some insanely curious folks will experiment with both. It’ll happen.