Here's an interesting experiment for you: guess what portion of the US economy is video games, movies, music, and consumer Internet services put together. Now graph that against "Of the last 20 people you talked to, how many are white men between the ages of 12 and 24?" I think that graph shows a markedly upward slope. I also think that it does not asymptotically approach the right answer.
You could do a spiritually similar experiment with, e.g., cosmetics/beauty aids, wedding services, etc and young ladies. Or healthcare, if you're looking for a gigantic underestimation.