Another estimate from a known crypto skeptic puts an upper bound at 3% illegal activity.[1]
> For example, illegal transactions, scams and gambling together make up less than 3% of volume.
Either way this 0.12%-3% range doesn't begin to approach the ~6%-12% estimated illegal volume for USD.[2]
[1]: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3942181
[2]: https://www.investopedia.com/articles/markets/032916/how-big...