Some quick research:
http://www.nber.org/papers/w3675
We estimate the consumption of alcohol during Prohibition using mortality, mental health and crime statistics. We find that alcohol consumption fell sharply at the beginning of Prohibition, to approximately 30 percent of its pre-Prohibition level. During the next several years, however, alcohol consumption increased sharply, to about 60-70 percent of its pre-prohibition level. The level of consumption was virtually the same immediately after Prohibition as during the latter part of Prohibition, although consumption increased to approximately its pre-Prohibition level during the subsequent decade.
I will assume this is Holy Writ, as I have no desire to look around for the data.
Let assume 1.00 (100%) is the level of consumption of any legal consciousness-altering product: ethyl, weed, meth, whatever.
Make it illegal, and use goes down to 0.65 (65%). "Hey, we just reduced consumption by 35%! Hooray for us! Ain't we smart! Let's have a toast (with sparkling grape juice) to just how witty we are when we're sober!"
Well, there are a couple of factors that indicate all that self-praise is only half right:
1. The 35% that quit are most likely the most law-abiding, straight-arrow of your citizenry. The fact that it is illegal is enough for them to say, "No, thanks." I would suggest that these folks never were a danger to others, whatever might be legal and culturally acceptable.
These are the kind folks that are mildly appalled that, in response to someone complaining about some location being illegal to CCW, others might reply, "Concealed is concealed."
IOW, you have gained pretty much zero WRT public order and quality of society.
2. The equation is not
1.0 + prohibition = 0.65
The equation is
1.0(mostly mild stuff*) + prohibition = 0.65(mostly hard stuff**) + more_crime + more_political_corruption + less_respect_for_law_in_general + less_liberty + more_taxes* If ethyl is to be prohibited: beer & wine
** If ethyl: distilled spirits
For instance, I can't imagine that the gang violence in the 1930's was anywhere near as destructive as drunk driving is today.
Wrong comparison. Is drunk driving
today anywhere near as destructive as
today's crack/meth wars in the inner cities and now rural areas?
This argument sounds good but does anybody really think that the Mexican cartels that are growing pot in California are suddenly going to go straight, incorporate themselves and start paying taxes?
No, they will be pushed out of the market by legal producers & distributors who will beat them like a drum WRT efficiency.
There will be fewer Mexican cartels & cartel members as there will be less money to be made in crime relative to legal work.