Josh and I wrote a model for Dr. Érdi's class which contains a community of drug users. Click on the image to read more.

WHAT IS IT?

The primary goal of the Drug Simulation is to model the
propagation of drug addiction through an infected population. The
secondary goal of this model is to determine whether making drugs
illegal or legal is more effective in preventing the spread of
drug addiction.

This model is based on a town with a population of 3,000 to 5,000
people. It observes the town over a short period of time,
approximately 5 to 10 years, and looks at the change in the
average-addiction of the town’s population in this time period.
Since the time frame of the model is so short the model assumes
that the population size doesn't significantly change. This
allows the model to focus purely on the effects of drugs and not
have to simulate the effects of population growth. The town has
the choice to make marijuana legal or illegal depending on which
they feel will best control its spread. Making drugs illegal
determines whether the town will combat the drug problem by
arresting the users or by trying to rehabilitate them. They also
have a sensitivity to the drug problem which determines how
forcefully they will come down on the drug problem.