That's only a tax in the very narrow sense that it keeps prison officers and policemen in jobs. I want the money to go towards general taxation. In Britain some £6bn is spent on cannabis each year. Taking a third of that in tax raises enough to reverse half of the chancellor's very controversial recent cuts to tax credits.
Where does the £6b number come from? It seems very high to me.
A 2014 survey has the following numbers: 31% have ever used illegal drugs, 21% still take illegal drugs "even if only occasionally". 93% of people who have tried illegal drugs have tried weed. [1]
Let's say the UK population is 65 million, that makes 13.65m "occasional or more often" illegal drug users, and if we assume that all of the 93% of those who have tried weed still smoke weed, that's 12,694,500 weed smokers. So with that number, to hit a total spend of £6B they would be spending an average of £472 each, or £9/week - I guess that's about 0.5-1g/week. I could believe that amount as an average among "weed smokers", but given the number includes people who say they do it "only occasionally", I suspect the long-tail means that £6b is unrealistically high.
That said, if you have a source for that I'd be interested to see more info.
However that's up to 6.6 billion for the whole illegal drugs market (not just cannabis). So the figure for cannabis would be much lower (see also that report).
