Generally, governments must provide a common regulatory or insurance standard and some release of liability, or at least a backing of the insurers, before a commodity market can begin trading. This is a major source of controversy in for instance the energy market, where desirability of different kinds of power generation varies drastically. In some markets, e.g. Toronto, Canada, surveys established that customers would pay 10-15% more for energy that was not from coal or nuclear, but strictly from renewable sources such as wind.