No, all I need to demonstrate is a country that saw no significant increase, not necessarily a decline.

From everything I know, the US states as well as the Netherlands that all decriminalized it in the 70s didn't see local use increase in significant numbers.

Neither did it in Belgium who did the same in 2003.

And before you go "decriminalization is not the same as legalization", in the "Making drugs illegal does not eliminate demand, but it absolutely curbs it." is clearly about drugs that have not been decriminalized at all.