Some cautions are in order when interpreting the results.
For example, young males with low education might be attracted to construction jobs because these are entry-level jobs that do not require a high school diploma. The association of high rates of drug use with construction jobs might simply reflect the demographic composition of this occupation, rather than a causal relationship. To sort out the inter-relationship among drug use, demographic characteristics, and workplace characteristics, it is preferable to use multivariate logistic regression, which are addressed in Chapter 6. There could be many factors driving this change. First, the distribution of establishments in general shows a slight increase in medium-size establishments from 42.7 percent in 1994 to 43.4 percent in 1997, and a slight decrease in the small establishments from 18.4 percent in 1994 to 17.4 percent in 1997.