Here is a very silly op-ed from a bunch of former drug czars, rightly mocked by the folks at reason.
From the conclusion to the Rand study:
The pretax retail price of marijuana will substantially decline, likely by more than 80 percent. The price consumers face will depend heavily on taxes, the structure of the regulatory regime, and how taxes and regulations are enforced.Those are reasonable and important conclusions and come along with a healthy dose of uncertainty. There just is not really any variation in the available data that looks like re-legalization. Marijuana was last legal in the US early in the 20th century and there were not a lot of social scientists around back then doing surveys on drug use.
Consumption will increase, but it is unclear how much because we know neither the shape of the demand curve nor the level of tax evasion (which reduces revenues and the prices that consumers face).
Tax revenues could be dramatically lower or higher than the $1.4 billion estimate; for example, uncertainty about the federal response to California legalization can swing estimates in either direction.
There is considerable uncertainty about the impact that legalizing marijuana in California would have on public budgets and consumption, with even minor changes in assumptions leading to major differences in outcomes.
Inside baseball: Peter Reuter, one of the co-authors of the Rand report, is a former colleague at Maryland and a very impressive fellow.
Hat tip: DeForest McDuff