Most countries are relying at least partially on the international trade of energy and will continue to do so. However, the issue of self-sufficiency does assume a particular significance in electricity markets, where a certain amount of domestic generation is required by the fact that electricity can neither be stored nor transported over long distances at reasonable costs. In island countries such as Australia and Japan or de facto geographically isolated countries such as Korea, domestic power generation must be able to cover demand on its own. This is not the case for storable resources such as coal or oil, where countries can enjoy high levels of security of supply even if they have no domestic production.