Fortescue Metals Group Ltd is an Australian-based iron ore miner. It has grown from obscurity at the start of 2008 to become the world's fourth largest producer. Growth was fuelled by debt, and margins are below the industry average. Expansion from 55 million tonnes in fiscal 2012 to 165 million tonnes in 2015 means Fortescue supplies almost 10% of global seaborne iron ore. However, with the iron ore market well supplied and longer-term demand likely subdued, we expect Fortescue's future margins to be below historical averages.