One of the arguments for banning adult legal access to drugs like marijuana (and even allergy medications) is that it helps to prevent abuse of these drugs by underage kids. This would be nice to test in a true control group setting, but we really don't have the opportunity under current laws to do so. But we can work by proxy. We can compare drugs that are illicit for everyone, like marijuana, to drugs that are legal for adults but not for minors, like tobacco.
If drug warriors are correct, teenage tobacco use should be much higher than use of other illicit drugs. This is particularly true because the proxy is an imperfect one, since the tobacco is a far less intimidating drug to try than, say, heroin. However, it turns out not to be the case. The new figures our out from our friendly US Government drug warriors, and it turns out that tobacco use is barely higher among teens than illicit drug use.
For example, the study shows that past month tobacco use among kids 12-17 was 12.9% in 2006, while past month illicit drug use in the same group was 9.8% (tables G.16 and G.7). That's lower, but certainly not decisively so. Both of these use numbers have fallen since 2002 at about the same rate.
Even more interesting are the figures for the number of kids 12-17 who had initiated use of certain substances in the past year (table G.26). In that year, 2.45 million had initiated cigarette use, but 2.79 million had initiated illicit drug use. Further, when asked if certain substances carried "great risk" in trying to purchase them, 68.7% of underage cigarette smokers said yes (table G.25). This response was 10 or more points higher than that of teenage occasional users marijuana, cocaine, or even heroin. In short, teenagers are saying it is more difficult and/or riskier to support cigarette use than it is to support a weekly marijuana, cocaine, or heroin habit -- exactly the opposite of the drug warriors' argument for prohibition (but consistent with the libertarian argument that bringing these drug sales above ground will make underage purchase more visible and easier to combat).