It should be age 25, at a minimum. With anything less than that, you're not following the evidence. That's if you're going to go down the legalization route.
If you're going to go down it, and it looks as though we are—I'm not for or against it, but I think you can read between my lines—then let's do it properly and put in place the data so that a year from now, or two years from now, we can measure the impact and we can course-correct.
Other countries will be very grateful to Canada for doing that, because Colorado hasn't really done it well and neither has Washington. The reason they don't is that policy-makers don't want to get the bad answers. The way you don't get bad answers is by not collecting the information.