Meth is one of the most vicious drugs and its use verges on a suicidal but it is the very depravity of the drug which should give those who would obdurately persist in the prosecution of this lost war on drugs pause to consider the hopelessness of the effort.
I have noted that when I see your name, an appropriate and well thought out commentary usually follows. Not so in this case. You have apparently bought in to the meme that the Libertarians have been pushing for the last sixty years; That the "war on drugs" is a failure.
This assertion is generally based on the fact that drugs are still available and that people are still using drugs. The implication being that if the "War" were a success, there would be no drugs or drug addicts.
Now I ask you, is this a realistic measure of success? Is the "War on Murder" a failure because we still have murders? Is the "War on Rape" also a failure because we still have Rapes?
I don't think anyone would argue that we should stop the "War on Murder" because we are still having murders. The Measure of success is that it keeps such crimes at a low level, and I will point out to you that drug addiction has been kept down to 2% of the population for 100 years. Usage is basically flat during that entire period of time.
Now some may argue that usage would be flat without any laws prohibiting drugs, but this theory conflicts with known facts in History. Usage goes up. It always goes up. Unless it is deliberately held down, it rises. Below is an example of what happens when drugs are legalized in a nation. You may recognize this trend as a "Logistical Growth function."
According to druglibrary.org, by 1906, half the adult population was addicted to opium. 50% is a very long ways away from 2% in terms of population.
In summation, I will reiterate that you are using an incorrect standard of success regarding the "War on Drugs." Legalizing drugs is a horrible idea. The fire is not an improvement over the frying pan.
When an addict murders someone in a mugging to fund his habit he is compensating for a system which makes drugs expensive and unattainable by other means (except perhaps by pushing and expanding drug usage). Thus the war on drugs victimizes the innocent and creates new innocent victims.
If criminalizing victimless behavior were in fact effective in controlling that behavior we would have stayed with prohibition, prostitution would not be the second oldest profession, and we would not be debating Internet gambling.
Criminalizing murder does not incentivize criminals to commit murder.
As you've said, "Till someone presents an argument that there are better figures, I will have no choice but to use what is available."
What's available says that addiction was low and declining in post-Civil War America: "In 1880 [...] there were over 400,000 opium addicts in the U.S. [...] By 1900, about one American in 200 was either a cocaine or opium addict." (http://web.archive.org/web/20110529221013/http://www.justice.gov/dea/demand/speakout/06so.htm) 400,000 in a population of 50M is one in 125 - ergo, between 1880 and 1900 addiction declined.