Does it count underage drinking? I didn't even notice that if it does. Regardless, around 85% of Americans use marijuana alone, so it wouldn't change the statistics by more than one or two percent. So I don't see how that would be misleading.
You're really misreading these statistics. Nowhere do they say anything close to "85% of Americans use marijuana".
On page 103, it says that 82% of fifty-year-olds (who attended high school during the heaviest-drug-using period in America's recent history) have used marijuana at least once in their lives. But only 10% of that same group have used it in the last year.
Among current 18-year-olds, only 42% have ever tried marijuana even once. And among most age groups under the age of 30, only between 23-34% have used marijuana within the last year.
However, I don't see evidence that the study you posted counts underage drinking in among illicit drug use.
"Nowhere do they say anything close to '85% of Americans use marijuana'."
I said 'have used' in my original comment, which is what I meant. (In my reply I was thinking lifetime prevalence, i.e. around 85% 'use' marijuana at some point during their lives. Poorly phrased, my bad.)
"Among current 18-year-olds, only 42% have ever tried marijuana even once."
The age of first use of marijuana is highly variable. By age 25 around 65% of people have used marijuana, and more people keep trying throughout the next couple decades of their life. The important statistic is what percentage of people use marijuana at least once in their lives, not what percentage use it on any given day.
"On page 103, it says that 82% of fifty-year-olds (who attended high school during the heaviest-drug-using period in America's recent history) have used marijuana at least once in their lives."
The 82% figure doesn't count people who didn't make it to fall of their 12th grade year in high school, so you actually have to adjust it up a couple percentage points. Also, even if less high schoolers were using illegal drugs for a decade or two, that probably won't have much effect on the overall lifetime prevalence. It might eventually decline a few points, but probably not that much.
85% sounds pretty wild. Hm, looking at pg 78 of the linked document, it says among people surveyed who were exactly 50 years old when surveyed, graduating in 1977, those who tried marijuana were 82%.
1977 has got to have been the historical peak of high school usage. I notice they don't mention 51 year olds or 49 year olds, they have specifically pulled out this one exact age for this statistic.
It then goes on to say that 29-30 yr olds have a 68% "adjusted" lifetime prevalence. What does that mean adjusted? It means the actual number they measured is lower (32% for 19-30 year olds), and they tweaked it upwards because they wanted a bigger number.
About this time is where I say a study has too many methodological flaws and should be disregarded.
Only 50-year-olds are mentioned because this is a longitudinal cohort they've been testing since 1977, and this year (2009) it's their turn to be reported.
The "adjusted" number is higher than the measured number because some people answered the survey ten years ago saying they'd tried marijuana in the past year but then in the current survey the same respondent said "no" when asked if they'd ever tried marijuana in their lifetime. So they're publishing both the actual numbers and the "we know you're probably lying" numbers.
"About this time is where I say a study has too many methodological flaws and should be disregarded."
Try actually reading it. It's really not that difficult to understand. The 'maturity recanting effect' section here also gives a brief summary of what they did and why:
I feel very comfortable stating with 100% certainty that your claim that the study said 85% of all people report being marijuana users (exact words: "around 85% of Americans use marijuana alone") was completely and outrageously inaccurate. It's humorous but a touch sad that you can't admit you were completely and utterly wrong. Lay off the stuff, clear your head, and re-read the report, dude.
It's also charming that you cite erowid.org as a reliable unbiased source. I am familiar with the site and have read it. It is a radical pro-drug site.
Where did he call them unbiased? (I would call them reliable, though they certainly have an agenda. But they've always struck me as working hard to present facts, or at least label opinion as such. Certainly I can't think of another site about drugs that I would trust over Erowid. And I would be very interested indeed to hear of deliberately misleading information posted there.)
I think Erowid is about as unbiased as it gets. All they do is provide information about drugs, they are neither advocating drug use nor condemning it.
Even their legal articles don't take any position on what drug policy should be, all they do is explain the case law that exists.
