If the population of dead drivers with over the limit THC is 40%, and this dramatically exceeds the population average, that would strongly suggest the THC level IS an indicator of either:
1. Impairment from THC, or
2. Worse than average driving and risk management skills in those who use the drug
1. Impairment from THC, or
2. Worse than average driving and risk management skills in those who use the drug