Do you have any evidence backed reason to believe it will?as by definition one country always has to have the highest, one country also has to have the lowest. Does that mean that magically it can't get higher because we're already number one? No.
http://alcoholism.about.com/od/sa/a/drug_use.htmI don't know that it won't go down if de-criminalized, but there is no evidence that it will either.
"Drug use is related to income, but does not appear to be simply related to drug policy, since countries with more stringent policies towards illegal drug use did not have lower levels of such drug use than countries with more liberal policies," said Louisa Degenhardt of the University of New South Wales.
"The United States, which has been driving much of the world's drug research and drug policy agenda, stands out with higher levels of use of alcohol, cocaine and cannabis, despite punitive illegal drug policies, as well as (in many U.S. states) a higher minimum legal alcohol drinking age than many comparable developed countries," the authors report.
"The Netherlands, with a less criminally punitive approach to cannabis use than the United States, has experienced lower levels of use, particularly among younger adults," the report says. "Clearly, by itself, a punitive policy towards possession and use accounts for limited variation in nation-level rates of illegal drug use."