Why the difference? Because in Australia's effort to be intolerant of drugs never overshadowed the importance of public health and disease prevention. At the dawning of the HIV/AIDS epidemic, Australia implemented an extensive network of syringe exchange centers across the country as part of their "Tough on Drugs" campaign.
According to syringe exchange poopoonants, providing syringes to addicts would have resulted in elevated drug use, elevated crime, and a very confused population of children who would be 'lured into drug use' thorough the sheer existence of syringe exchange programs. But that is not what has happened. Australia has one of the lowest HIV/AIDS rates in the world, and while nothing to brag about, their IV drug using population is the same size as Texas', a state with out legal access to syringes.
So, what affect does syringe access have on the size of IDU populations? Apparently none.
What affect does a lack of syringe access have on IDU populations? Lots of AIDS and hep C.
Texas has the 4th highest HIV/AIDS rates in the country that boast having the highest HIV/AIDS rate out of all industrialized nations! And, over 400,000 Texans are infected with the deadly HCV virus. Hasn't anyone heard that our health care system is in crisis? These diseases are expensive and cost us around 100g's a pop. Last I heard, a syringe cost 7 cents.
For more information on Australia's successful SEP's, check out their 2002 report that details how many HIV and hepatitis C cases have been prevented, how much it cost the government, and how much money it saved them.
For information on Texas HIV/AIDS rates, check out the Department of State Health Services annual surveillance reports.