But, looking forward, most obviously in the case of iron ore, there is not so much supply to come on to the market, so the commodity price dynamics are very much dependent on the demand side of the market. In the near term, the prices of coal and iron ore are primarily affected by Chinese demand.
There is analysis on this issue in a box in the recently published . It is  Statement on Monetary Policy  worth keeping in mind the simple point that maintaining the level of demand around current levels http://www.rba.gov.au/speeches/2017/sp-dg-2017-11-13.html  4/13  13/11/2017  Business Investment in Australia | Speeches | RBA  will support prices if there is no material change in supply.