This estimate is especially interesting because of the methodology. It's well worth a read.

2017
> In other words, more than a third of all US currency in circulation is used by criminals and tax cheats.
>
> https://www.aier.org/article/how-much-cash-is-used-by-criminals-and-tax-cheats/

0xbitcoiner

Ah, okay! There must be some studies out there with this data. I'll do a quick search.

charts

Chainalysis Estimates 0.34% of On-Chain Crypto Activity is Illicit

It's perplexity.ai (which I use more than google these days) so it learned this gestalt answer from crawling the web, and cites some sources but doesn't seem like there's any great data out there... (the sources linked seemed rather hand-wavy)

https://www.perplexity.ai/search/what-is-the-CB96wV71QRqe429V.e51Lg#0