A report by PwC on the top 40 global mining companies by market capitalization revealed Tuesday that while production volumes rose by 6% in 2012, falling commodity prices meant that revenues were flat at $731 billion, making it the second year in a decade that mining revenue did not rise year on year.

PwC's annual report of global trends also shows that global miners profits fell 49% to $68 billion last year, driven by weak commodity prices and cost pressures, with Australian companies hardest hit because of higher labour charges.

In yet another account of the poor performance the mining sector had last year, PwC's reported the world's 40 largest miners — a list that includes Australian giants such as BHP Billiton (ASX:BHP), Rio Tinto (ASX:RIO), Newcrest (ASX:NCM) and Fortescue (ASX:FMG)— announced a massive $45 billion in writedowns during 2012.

At the same time, their return on capital employed – a ratio that highlights the profitability of a company's investments – slumped to a decade low.

The report also noted an unprecedented change in chief executives in the past 12 months, with 50% of the "top 10" chief executives being replaced since April 2012.

Despite the challenges for the mining sector, PwC concludes long-term demand for commodities remains healthy. "Now is the time to show that the industry can deliver in good times and bad," the report says. PwC said it was also optimistic about China's outlook as the most important customer and the future emergence of Brazil, India and Indonesia.