The latest public CIA World Factbook numbers estimated that the percentage linked to crime was 3% to 5% of the world's entire GDP. BTW the CIA should know something about it...

In other words, whether they know it or not, every single bank in the world is involved in money laundering.

P.S: I don't know if that's true or not but some people have made the case that there are, percentage-wise, less transactions linked to crime on the public, transparent, ledgers that are the blockchains than in the real banking system.