The figures from open university.
But you're right to an extent. There's a statistic black protest groups like to quote which is something like 80% of drug users are white and 60% of people locked up for drug use are black.
Which sounds shocking but is just because most of those white people are on weed which is a lower rated drug than heroin and cocaine.
Funny that, my white friends are waaaaay more into class A's than my black friends.