The company-operator of the cryptocurrency fund Grayscale conducted a research among American investors to find out their interest in cryptocurrencies.
"Bitcoin 2019 Investor Study" by Grayscale showed that from a pool of 1,100 American investors, more than a third (36%) of respondents consider investing in Bitcoin. If we assume that there are about 63 million investors in the USA, then the interested people represent a potential audience of more than 21 million people.