reserve bank, page-6

T1...
I think You are wrong Mate!! 20 years in the industry seeing the management change and You can look at last years report too.
Taken from BHP's 2010 Annual report!!! :

The US dollar is the currency in which the majority of our sales are denominated. Operating costs are influenced by the currencies of those countries where our mines and processing plants are located and also by those currencies in which the costs of imported equipment and services are determined. The Australian dollar, South African rand, Chilean peso, Brazilian real and US dollar are the most important currencies influencing our operating costs.

In BHP?s 2010 annual report, the affect of USD movements were summarised thusly:

Local currency costs were well controlled across the Group; however, the weaker US dollar had a negative exchange rate impact of US$2,150 million.

This $2.15B loss is against a total FY10 EBIT of $20B ? so currency movements ate up just over 10% of EBIT.

So, in a year when the AUD moved from $0.80c to $0.90, then dropped back to $0.85 US cents, BHP lost 10% in EBIT due to currency movements. The range of the FY10 movement was about 12.5%.

By contrast, the AUD has moved from about $0.85 to a peak of about $1.10US in FY11 ? a movement of 29%. (Bigger profit chunk this year Timely1!)

So what I am trying to say is that big upward movements in the AUD can result in big downward movements of BHP (and most other major Aussie miners) profits.