Once marijuana's legalised, tokers worldwide would smoke their own home-grown (not that they don't now) at a much larger, unfathomable scale than the current scenario. Growing the plant(s) requires proper lighting, temperature, soil and care. All the effort put into it right now goes to waste because of friends, family dropping by who do not approve of the herb, which forces the grower to dump the saplings, plants elsewhere, to wither and die.

Home businesses would thrive on marijuana as the investment isn't huge and consumer expectation is simple. Clean? Sold!!

Homemakers & the i-hate-corporate-life population would be able to generate revenue, thanks to their "green" thumbs. Since gardening is invovled, manure, fertilisers and tools are obviously, too.

Hence proven, legalising marijuana would not just result in growth of the agro industry but also increase employment, tax revenue, relieve a lot of friends and family about toker's habits AND reduce drunken driving, making the streets safer for the stoned population to lurch about.