From the 2008 National Survey on Drug Use and Health:
How much do people risk harming themselves physically and in other ways when smoke marijuana once a month?
While the question used to obtain baseline data takes into account all kinds of harm, some respondents may focus on physical harm only. Consequently the measure is a very conservative estimate of the perceived harm. A description of NSDUH was published by SAMHSA.
Baseline data has been revised from 33.9 to 33.4 percent. As a result, the target has been revised from 37.3 to 36.7 percent