The world's biggest miners lost $156 billion of their combined market value last year, according to new data, and a depressed commodity price outlook could keep the losses flowing.
Market capitalization for the top 40 miners stood at $791 billion at the end of 2014, a 16 percent drop from 2013 and a halving in value from four years ago, PwC said in a recent report.
"Miners will need to need to stay on the defensive and in lean, fighting form, as they bob and weave through a number of ongoing challenges ranging from slumping commodity prices and volatile markets, to growing pressures from government and shareholders," PWC said.
The plunge in market value follows a downturn in resource prices over the past year. Iron ore prices have sunk over 30 percent, Brent crude dropped 44 percent and among base metals, gold declined 7 percent, while platinum fell 25 percent.
Meanwhile, assets of the top 40 group declined by 1 percent in 2014, compared to an increase of 7 percent in 2013, driven by $26 billion fewer capital expenditures, the report added.
Among the 40 miners ranked, BHP Billiton, Rio Tinto, China Shenhua Energy, Glencore, and Vale were among the top five while Zhongjin Gold, Shandong Gold and China Northern Rare Earth Group were at the bottom.