The main problem with the paper is that it keeps discussing from the "War on Drugs" angle, even though it acknowledges early (from its very title onward) that this is not the main contributor to the huge prison population. It's hard to find an answer to the question which immediately follows, "OK, what is the cause, then?" And then it turns out that through indirect effects, in fact WOD might be a primary driver all the same. Confusing.
Can you be more specific about which of the author's conclusions point to drug prohibition being the primary cause of incarceration, just indirectly? That's not the conclusion I got at all.
The conclusion I inferred was that prosecutors are running amok across the whole gamut of possible crimes.