Here the question is already worth raising: who has not heard about bitcoin? These 20% who have not heard most likely live in the deep wilderness and they are not interested in the news. My grandmother in Ukraine knows about "Beethoven" So there is nothing surprising in the growth of popularity of cryptocurrency. Since last year it was well covered in the media.
The remaining 20% are probably the elderly or people in rural areas without an internet connection. I do think there is still a relatively high amount of areas in the US where you cannot get a fast, reliable broadband internet connection. What I am more interested about is finding out how many people in other countries have heard about Bitcoin. I wonder if it was as popular in other countries like it was here in America.