"The plant hasn't changed, the consumers haven't changed," says Auburn University's Mark Thornton, "it's prohibition and the difficulties and risks of getting it from the growing stage to the consumer."

Thornton, author of The Economics of Prohibtion, sat down with ReasonTV's Tracy Oppenheimer to discuss how prohibition distorts the market for marijuana, and why potency levels are on the rise. He says that the potency of other illegal drugs has also increased and that this even included alcohol during prohibition.

"It's a phenomenon that exists anytime government tries to prevent the consumption of something."

About 5 minutes.

Produced by Tracy Oppenheimer, Cameray by Alex Manning.

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