Just banning something does not prevent it from happening

Tim Harford writes,

Nowadays we realize it is insanity to suppress markets for coal and steel, but we are still tempted to try the trick on the markets for sex, drugs, rhino horn, soccer tickets and, apparently, Mars bars.

These efforts usually fail. Tickets for big sporting events such as the World Cup or the Super Bowl are a bit like Soviet coal. They are supplied in a non-market system or sold at below-market value for political or ideological reasons. Although scalpers perform a social service by getting tickets to those who value them most, nobody likes them because they are bearers of bad news: These events are popular, supply is limited, and consequently the price is high. Markets are good at telling us this sort of truth, and the ticket agency Ticketmaster is starting to use online auctions to beat the scalpers at their own game.

Markets for prostitutes and for rhino horn are suppressed for a different reason: They are thought to be bad for prostitutes and rhinos, respectively. That is obviously true for individual rhinos and is true for unwilling prostitutes too, but just banning something does not prevent it from happening. Julian Morris, now director of International Policy Network, a free-market think tank, studied the rhino-horn ban and concluded that it had reduced rhino numbers by discouraging sustainable management of rhino herds in southern Africa, while doing nothing to prevent poaching in east Africa.