If Bob transfers $10 back and forth between both of his bank accounts 99 times and then buys $10 worth of crack, would you say that 1% of Bobs money was used for illegal purposes or 100% of it was used for illegal purposes? Depends on what specifically you're trying to measure.
There are two things here that are simultaneously true:
1. A small percent of BTC transactions are for illicit purposes.
2. A large percentage of the goods and services purchased with BTC are illicit.
If Bob transfers $10 back and forth between both of his bank accounts 99 times and then buys $10 worth of crack, would you say that 1% of Bobs money was used for illegal purposes or 100% of it was used for illegal purposes? Depends on what specifically you're trying to measure.
There are two things here that are simultaneously true:
1. A small percent of BTC transactions are for illicit purposes.
2. A large percentage of the goods and services purchased with BTC are illicit.