The United States and Canada, like other northern industrial nations, are under considerable economic pressures to develop their indigenous resources of oil and natural gas. Incentives for exploration and development are provided by increases in the price of fuels on world markets and political instability in the Middle East, the major alternative source of supply. The Arab oil embargo of 1973–74 quadrupled prices per barrel from US$3.00 to US$12.00 in less than a year; since then the price on world markets has trebled and remains unstable. Searches for new sources of energy in the far north have led firstly to the discovery of major shore-based fields (for example those centred on Prudhoe Bay), and the extension of old ones (Norman Wells), and more recently to important developments off-shore. Many new sites are now being explored, and to date over two billion dollars have been spent by the US and Canada, to find and develop Arctic offshore wells. As yet not a cent has been earned in return, largely because there are at present no means of delivering the petroleum from offshore sites—no safe and reliable system of transportation equivalent to the pipelines from shore-based sites. Industry and government are considering alternatives, but no full-scale construction or procurement programmes have yet been launched.