The statistics are interesting, but they kind of miss the GGP's point. Decriminalization is not legalization. If you just decriminalize, drug users still have to buy their drugs from sketchy black-market suppliers. That's very dangerous compared to buying from a legal, regulated industry. For example, alcohol is predictable and pure today but in the prohibition era, when all suppliers were criminals, it wasn't [1][2].
[1] http://content.time.com/time/specials/packages/article/0,288... [2] http://www.slate.com/articles/health_and_science/medical_exa...