coal mining companies representing around 80 percent of Indonesia's output were surveyed by PwC .
decline in Coal miners' profitability in 2014 from 2011.
drop in spending in 2015 from 2012 levels due to declining profits. This has resulted in reduction in exploration of new mines and rejection of mines with dirtier coal.
tonnes of coal reserves were identified by Indonesia in 2014.
tonnes of coal reserves that mining companies consider as economically retrievable due to declining profitability and inability to spend more on cleaning dirtier coal.
year by when the 8.3 billion tonnes of economically retrievable coal reserves will be depleted based on current demand, if no new reserves are identified.