I am in favor of decriminalizing marijuana and dont believe people should be put in prison SOLELY for drug use. The reality though is...that they are not. Those in prison on drug related offenses are in the vast majority there due to distribution/sales, or the commission of a criminal act while on drugs. Possession sentencing laws vary, depending on amount held for personal use vs amount held that meets criteria for intent to distribute. The type of drugs held is also relevant. Marijuana possession sentences are usually minimal, seldonw reaching prison (most end in county jails of there is a sentence called for), while heroin and cocaine and meth tend to merit much higher sentences.
Just saying "end the drug war" is not the prison panacea people think it will be.
What I will stipulate is the stats on this, and how they are cut up, are all over the place on this. By government stats alone decriminalizing drugs and releasing possession and distribution charges only would put us somewhere in the 25% to 35% range, if we separate out federal from state (and local) we seem to end up somewhere in the 15% to 25% range.
When I rather whimsically said "half the problem" what I am referring to is the socioeconomic impact of what the "War on Drugs" has done to this nation.
What that really means is the development of a subculture (for lack of a better way to put it) within society that ends up branded with several lifelong consequences from being in some phase of the criminal justice system, a very long way of saying we send way too many people down an economic and/or racial disproportionate path with few possibilities of return. Any sociologist or criminologist will talk about likely behavior once someone goes into that life and the likely behavior once part of the prison system. Since we've started this mess we've had an almost 400% increase in our Prison population and it is a bit asinine to divorce Drug related crimes from all others on the assumption they are divorced out there in this subculture I am talking about.
I would agree on the surface that the numbers when applied purely to charge and sentence skews the results, but it also makes us ask what criminal motivations are reduced when we take away the realized results of this so called War on Drugs.
We have spent roughly 50 years on this effort and the results are staggering. Before we were not even in the top 20 among comparable nations in incarceration rate, we now lead the planet in this area dwarfing nations including Cuba, Russian, China, Iran, Turkey... everyone. Arrests for Drug related crimes has almost tripled (even if they all did not end up with some lengthy sentence in a federal prison somewhere.) We are in the $Billions per year dealing with the costs of fighting the war, prosecution of those caught, and ultimately housing those found guilty.
When someone asks how to reduce prison costs and populations, the answer is looking to what failed society.
The War on Drugs did not make us safer, did not reduce crime overall, did not reduce drug demand (usage,) and did not improve our society. If anything, it took a portion of the nation and made them targets and by most measure removed them from mainstream society.
What we know as a War on Drugs was really a targeted war on certain people. It took those without much means, disproportionately included minorities in that group, and criminalized them to the point of creating this subculture. We know now that certain communities are targeted, and that reflects in the results. The AMA will tell us that economics impacts drug use far more than race, yet minorities are 3 to 4 times more likely to be policed and arrested for a drug related crime. Well over 60% of the prison population are minorities, and it is worse when considering drug related crimes.
Ultimately my point is sociology tells us ending the War on Drugs solves other issues, because it addresses a fault in thinking almost 50 years old producing no measurable success other than removing a significant percentage of the minority population from mainstream participation.