observations of what I see my colleagues and co-workers order & drink, what I see listed on menus, what I see stocked on shelves in supermarkets and convenience stores, etc. I did a very quick google search, and it did not appear that data was readily available, and I'm not interested enough in this topic to invest a lot of time researching data to prove an unimportant point.

However, I would be shocked if sales of decaffeinated colas were not significantly lower than sales of decaf coffee. If you have data that shows otherwise, I would be interested in seeing it.