—and this small “l” libertarian agrees, also—and also suspects that there was less of a “drug problem” in 1880 with no prohibition, than there is now-—
According to figures at the USDOJ website, addiction to cocaine and opiates was actually higher in 2000 than in 1900.
"By 1900, about one American in 200 was either a cocaine or opium addict."
--http://www.usdoj.gov/dea/demand/speakout/06so.htm
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"Among those using cocaine in the United States during 2000, 3.6 million were hardcore users who spent more than $36 billion on the drug in that year."
--http://www.usdoj.gov/ndic/pubs07/794/cocaine.htm
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"There were an estimated 980,000 hardcore heroin addicts in the United States in 1999, 50 percent more than the estimated 630,000 hardcore addicts in 1992."
--http://www.usdoj.gov/ndic/pubs07/794/heroin.htm
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The US population in 2000 was about 280,000,000. So using those figures, the combined addiction rate was about 1.6% in 2000 vs 0.5% in 1900.