Get your ore in. The iron ore price has fallen by more than a third in the past year to $115 a tonne, although China is still buying up whatever Rio Tintocan produce, in spite of the country’s managed economic slowdown. Rio, with its multi-decade investment horizons, plans beyond short-term price variations. China’s slowdown could be shortlived if stimulus measures kick in during the fourth quarter. But Rio, which derived nine-10ths of its $5.2bn of underlying half-year earnings from iron ore, cannot be complacent: it is more exposed to the iron ore price than peers.

The near one-fifth drop in earnings before interest, tax, depreciation and amortisation to $8bn reported on Tuesday was almost entirely caused by the fall in iron ore. Contracts are at different prices and durations but, assuming steady fixed costs and other things being equal, a further one-third fall in the first-half average price of about $138 a tonne would roughly halve Rio’s ebitda to $4.2bn.

For now, however, Rio is sitting pretty: it can mine the stuff and land it in China for $37 a tonne, assuming a freight rate of $7 a tonne. BHP Billiton’s figures are broadly similar. Unlike Anglo Americanand Xstrata, Rio shows no sign of dabbing the brake pedal on capital expenditure as it invests in increased output in Australia’s Pilbara region. Record first-half ore production and sales partly compensate for falling ore prices. Nor, with annual cash flow from operations at $7.8bn, is $7.6bn of capex a stretch. True, net debt rose 55 per cent to $13.2bn to fund capex, acquisitions, the dividend and share buybacks, but it is still below 1 times annualised ebitda. If prices keep falling, Rio should rethink its capital management and cut debt.