Art Carden writes,
“But these drugs are so dangerous!” people might contend. Indeed, they are. But this overlooks the fact that drugs have increased in potency as a response to government crackdowns. Which would be easier to smuggle: $1,000,000 worth of marijuana, or $1,000,000 worth of cocaine? $1,000,000 worth of cocaine can be packed into a much smaller space than $1,000,000 of marijuana. If we decide to fight drugs, what is likely to disappear from the market and what is likely to end up all over the market? Low-potency drugs are likely to disappear. High-potency drugs—like higher-potency marijuana—are likely to stay. According to Milton Friedman, “crack would never have existed. ... if you had not had drug prohibition.”So in a effort to drive all drugs out of the market the government has has only succeeded in creating a situation in which more dangerous drugs are driving less dangerous drugs from the market. Certainly a very "adverse selection".