21 to 29-year olds use alcohol 5:1 over marijuana [...]; the legal-for-adults drug is proportionately less used by teens. [...] If the only explanation for the disparity in the two alcohol-to-marijuana ratios is that adults steer away from the illegal substance, then it would follow that if marijuana was relegalized for adults, the adult alcohol-to-marijuana ratio would become the same as for teens---that is, [...] relegalization would increase 21-to-29 marijuana use by 2-1/2 times. [...]That seems clearly ludicrous---leaving only the conclusion that the adult legality of alcohol does make it less used by kids than it otherwise would be.
Only if we accept that illegality is the only factor in reducing use for this age group. I think illegality is one factor, yes.
What are the others?
Right now, I'm not concerned about this age group.