In response to such concerns, the Bush administration ordered a study in 2003. It found that only 15 percent of oil and 12 percent of natural gas beneath federal lands in the West is totally unavailable because it is in such places as national parks, wilderness areas and critical habitat for endangered species. About 60 percent of oil beneath public lands is in areas where it could be developed with normal permits — also meaning 40 percent is in difficult or impossible-to-develop areas.

Environmental groups argue that exploration into sensitive areas is not needed and would have minimal impact on gasoline prices. For example, The Wilderness Society argues that even 20 years down the road, when the Arctic wildlife refuge would be at peak production if drilling is allowed there, it would affect gas prices by only about a penny a gallon.

However, the Energy Information Agency estimates that at possible peak production in 2025, the Alaska refuge would significantly decrease U.S. dependence on foreign imports. Without the Arctic National Wildlife Refuge, it says America would import 68 percent of its oil. With that area in production, it would import 64 percent.

Cutting competition

Increased competition usually lowers prices. But big oil companies have made huge mergers in the past decade, reducing competition. Senate investigators, for example, say that is one big factor in higher gasoline prices today.

Among the mergers:

• In 1998, British Petroleum (BP) merged with Amoco.

• In 1999, Exxon merged with Mobil.

• In 2000, BP/Amoco acquired ARCO.

• In 2001, Phillips announced a mergerwith Conoco, and Chevron (which had acquired Gulf in 1994) acquired Texaco.

Senate investigators said it found that companies "attempt to achieve and maintain a tight balance between supply and demand" to keep prices high and are more able to do so with the currently decreased competition from mergers.

For example, they said that in California, "Six refiners own or operate about 85 percent of the retail outlets in the state, which account for more than 90 percent of the retail gasoline sold in the state. As a result, the few large refiners in the state have the ability to affect the price of gasoline through their individual supply decisions."

Zone pricing

Senate investigators said they found another practice by big oil companies and their refiners designed to reduce competition — this time among local distributors, or gas station chains. It is called zone pricing.