Houston, America’s fourth-largest city, is poised between the joys of cheap fuel and the pain of the industry which produces it. Dave Lesar, chief executive of Halliburton, which provides drilling and pumping services, says its customers are cutting spending by 25-30%. On January 21st BHP Billiton, a giant miner and oil producer, said it would cut the number of its onshore oil rigs in America by 40%. A so-far modest fall in the total number of active rigs (see first chart) is set to accelerate.