Rio reduced its stockpiles by almost 8 million tonnes during the year, while BHP Billiton sold about 2.3 million tonnes more iron ore than it mined over the past six months. Fortescue Metals Group chief financial officer Stephen Pearce said he wanted to follow suit in 2015. "The main focus for me in this next six months is mine stocks ... and as I have flagged we would like to take another $100 million to $200 million out of that by June of this year," he said. The tactic can allow mining companies to temporarily slow the rate of their mining operations, thereby reducing the cost impact of the most expensive part of their business. But the focus on "working capital" has gone much deeper than simply running down ore stockpiles.