I think that’s only part of the equation. There also must be many people who hear about a product or service on some media and then sign up later without rememb

I think that’s only part of the equation. There also must be many people who hear about a product or service on some media and then sign up later without remembering the code (or that the podcast was the reason they are doing it). You could have a “how did you hear about us” question, but those are annoying.