Actually, the USDOJ puts the addiction rate at about 0.34%:
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.
-- www.usdoj/ndic/pubs07/794/heroin.htm
Link should be: http://www.usdoj.gov/ndic/pubs07/794/heroin.htm