Remember that the e-cigarette business is larger than just the direct sale of the product to consumers, it also has a tangential influence in other markets. Obviously these additional influences vary depending on the size of the economic activity, but right off the bat you can categorize some of them into broad spheres:
Business to business activities:
- Print materials (e-liquid labels, print shops (or specialty printer manufacturers), physical print material (brochures, adverts, business cards, other promotional printed material), and locally manufactured boxes, packing material, etc.)
- Raw material purchases (ingredients and material sourced domestically)
- Digital media (web hosting, online advertisements, TV/Radio advertisements)
- Retail (Retail furnishings)
Mixed (Consumer & Business) activities:
- Events (hotel/hosting revenue, local tourism, travel revenue)
Localized Business activities:
- Employment (direct staff, payroll taxes, insurance)
- Security (Security devices, Security Services)
- Taxes (Business (State & Municipal) taxes, income taxes, licensing taxes (where applicable))
So while you'll probably find some information on the size of the industry with Forbes and Wells Fargo, these additional categories may or may not be contemplated within their figures, and events, such as ECC or the smaller Vapebash/VaperCon/Vapefest/etc, generate a significant amount of revenue for the cities that host such events (through hotel taxes and localized tourism, which supports local businesses). Mapping out these ramifications takes a lot of time, but it can help paint a more complete picture of the impact.