Even as support for the legalization of marijuana has doubled, the use of it among the 18-29 year-old set is actually on the decline. That’s according to a Gallup poll, that says 36% of that age group has tried marijuana. Compare that to 46% in 1999, and 56% in 1985, and you’ve got a compelling argument against the common assumption that kids these days are crazier than ever. That said, the actual number of people who do use marijuana is actually holding fairly steady. It seems like people are just waiting a little longer before they start actually using it …