In 2012, Colorado and Washington became the first states to legalize marijuana for recreational use, and have since been joined by Oregon, Alaska, and Washington, D.C. In 2014, Colorado is reported to have received over $50 million in tax revenue from the sale of recreational marijuana, much of which was slated to be used for school construction. The potential for increased tax revenues and the benefits these revenues can provide has a number of other states contemplating the possible legalization of recreational-use marijuana.
Recall that efficiency means producing what people want at the least cost.