The number of U.S. oil-drilling rigs, a proxy for activity in the oil industry, had fallen sharply amid a 14-month tailspin in oil prices as surging U.S. production and an unwillingness by the world’s cartel to reduce production led to a global glut. U.S. oil prices set a six-year low Thursday as concerns about global economic growth, a stronger U.S. dollar and a major U.S. refinery outage weighed on the market. Total U.S. rigs are down 1,029 from a year ago, with oil rigs down 917, gas rigs down 110 and other rigs down by two, Baker Hughes said, though the pace of declines has slowed. Meanwhile, two gas rigs were taken off service in the latest week, bringing the total down to 211. The U.S. offshore rig count was 35 in the latest week, down three rigs from the previous week and 27 from the year-ago period.