[OkayPhysicist]

50% of under-21 college students engage in underage drinking. The number for of-age students is even higher. 44% use cannabis. We can safely say that those two groups overlap significantly, but barring people who consume either dramatically cuts back on your potential pool.

[xNeil]

Per my experience, I can't attest to that of cannabis, but the percentage of students drinking alcohol underage is significantly higher than 50% in every college I have heard of or visited.