The myth of rising marijuana addiction rates

So today I clicked on one of libertarian econoblogger Tyler Cowen's Assorted Links entitled "What Obama needs to know about drugs," which took me to this site. Basically it's a primer on where drug use and policy is at right now. But I was struck by the fact that someone who purports to know something about drug policy would write the following as number 5 on a 22-point list:

5. Cannabis prevalence holding steady. Age-at-first-use still distressingly low (middle school). Increased numbers of treatment entries, perhaps due to higher potency and/or higher ratio of THC to cannabidiol.

The author, Mark Kleiman, buys into a few anti-drug propaganda myths here. The first is that marijuana treatment center admissions track anything but the propensity of the American legal system to force people to go to them. The DEA tries to make you believe that this is indicative of higher rates of addiction, but the facts belie the truth. The vast majority – from at least 58% nationally in 2005 to 69% in Texas between 2000 and 2005 – are sent to treatment by courts. This is partially to do with the innovation of drug courts, which are more likely to send someone to treatment than jail, community service, a fine, or simply letting them free.

The second piece of propaganda that Kleiman believes is that higher potency marijuana is anything other than a harmless reaction to marijuana's illegality. Because laws base their punishments on the weight of marijuana regardless of potency, the risk associated with growing/trafficking/selling $10,000 of high-grade marijuana is lower than the risk of doing the same with $10,000 worth of poor quality pot. The prices reflect this, and even though some might prefer lower-quality weed (just like many people prefer beer over hard liquor), it makes economic sense to buy the higher quality pot. But even beyond that, simply buying higher quality marijuana doesn't mean someone will necessarily ingest more of the substances that get you high. Just like people titrate their use with alcohol (everyone knows that a glass of beer has as much alcohol as a glass of wine or a shot of liquor), people titrate their marijuana use, smoking as much (or little) as it takes to get high.

And finally, what the hell is "age-of-first-use still distressingly low (middle school)" supposed to mean?? Hopefully he doesn't mean that the average person begins smoking pot in middle school, because that would make him very wrong. Maybe he means that some people start using marijuana in middle school?