economist.com

“THE president holds the key to addressing the pain… at the gas pump,” said John Boehner, Republican Speaker of the House of Representatives, in early April as petrol prices approached $4 a gallon. “My question for the president”, he continued, “is: what are you waiting for?” For the right moment, perhaps. Since April petrol prices have fallen more than 50 cents, or almost 13%. The trend is expected to continue; prices could dip to near $3 a gallon this summer, the lowest level since January 2011, well before the turmoil of the Arab spring.

Despite angry Republican rhetoric, the president has little control over prices at the pump. Credit for the surprising recent turnaround in petrol costs rests mostly with the market for crude oil. American petrol prices closely track trends in the benchmark cost of Brent crude, which sank from nearly $130 a barrel in March to just over $90 a barrel now, a 28% decline. Oil prices feed through to petrol costs, with a lag. Continued falls in crude prices in recent weeks explain why further drops in petrol prices are expected.

Cheaper oil, too, is the result of factors far beyond Mr Obama’s reach. A small share of the recent tumble—about five percentage points’ worth—is domestic in nature, but even so it is not a result of government action. In May, Enbridge, a Canadian company, reversed the flow of a big North American oil pipeline, sending a glut of oil from America’s northern plains southward to coastal refineries. Yet the lion’s share of oil-price weakness is a by-product of an increasingly shaky global economy. With the euro zone in recession and growth flagging in America and China, the world’s three largest consumers of oil are buying less of it than expected in early 2012