I see what you mean and stand corrected; I wasn't assuming the case where the product sells without advertising at all. From a gut feeling I can say that the c

I see what you mean and stand corrected; I wasn't assuming the case where the product sells without advertising at all. From a gut feeling I can say that the customer came from some result of previous advertising (as we're talking about products like sodas not life-essentials like oxygen), but I guess there's no way to know since those previous ads being tv/print ads were not tracked. If we suddenly stopped all other forms of advertising and only used online ads, in 10-20 years each customer can be tracked exactly to what ad created the first impression about the brand and thus be more accurate (still excepting marketing like word of mouth though)