Energy independence is a hallowed aim for America. On this, unlike most other issues, Barack Obama and Mitt Romney can agree.
"I'll get America and North America energy independent," Mr Romney vowed in the second presidential debate. "I'll do it by more drilling, more permits and licenses," he added. "I'm all for oil production," countered Mr Obama. The president gives renewable energy a more prominent role in his plans to achieve energy independence, although on his watch the U.S. has experienced a remarkable oil and gas boom.
The allure of becoming self-sufficient in oil is clear, given that the U.S. is the world's largest petroleum importer while most of the world's crude is concentrated in places hostile to the West, unstable or a combination of the two. Still, the benefits of oil independence are overstated.
As a result of elevated prices, which stoke public anxiety about energy security, something revolutionary is happening. Oil that used to cost too much to extract is now a profitable prospect. Breakthroughs in horizontal drilling and hydraulic fracturing ("fracking") make tapping these reserves possible. Widespread extraction in the U.S. of shale oil -- crude oil trapped in tight rock formations -- combined with the prospect of increased output from the Gulf of Mexico, offshore California and possibly Arctic fields, is fuelling the talk about U.S. oil self-sufficiency.
Viewed simplistically, domestic supplies should be cheaper than imports. Transport costs are lower and tariffs are avoided. Cutting reliance on imported oil could reduce inflation risks, too, by giving U.S. policymakers more control over oil prices. Unfortunately, the reality is different.
Oil is a global good. Unlike gas, it is easily transported and therefore easily traded. Prices are set internationally: the price of a barrel of American oil is influenced by distant factors such as supply from Angola and demand in Australia. Even if the U.S. was awash with millions more barrels of oil, the price of domestic crude would not be set in isolation.
Were prices in the U.S. to dip dramatically, oil firms would seek more attractive markets abroad: it is illegal to sell U.S. domestic crude overseas, but products refined from it, like diesel or gasoline, can be freely traded. Exporting more American petroleum products would thus make domestic supplies tighter, forcing up prices at home. Also, studies show no statistical correlation between the volume of home production and the prices Americans pay at the pump. And even if the U.S. managed to churn out far more oil, because prices are set on global markets, safeguarding sea lanes would remain a priority. America is locked into projecting power overseas.
Without a doubt, the U.S. would gain some advantage from increased self-sufficiency in oil. Reducing oil imports could help to shrink the trade deficit: petroleum products comprise nearly a fifth of all U.S. imports. There would be an even greater benefit to the trade balance, meanwhile, if gushing U.S. oil output led to more exports of higher-value refined petroleum products. Improvements in the current account would reduce America's borrowing needs and lead -- all else equal -- to a stronger dollar.
This is a far cry from the terms of the present debate. Whatever the hype in the U.S. about oil self-sufficiency and its benefits to energy security, America is a long way from achieving oil independence -- let alone energy independence. And even if the country one day found oil self-sufficiency within reach, the benefits would fall well short of the promises made by politicians on the campaign trail.
Martin Adams is Energy Editor for the Economist Intelligence Unit.