All that Trump campaign chatter about making America great again has done wonders for the US dollar. This past week the greenback hit new 13-year highs. Another asset class having a storming year: shares in mining companies. The MSCI world metals and miners index is up 90 per cent from its January low. Yet history suggests the two cannot rally in tandem for long.

The surge in metals and miners is largely down to China. Demand there is key to most metals, not least steel. At the start of this year, worry-worts moaned about an imploding Chinese steel industry exporting cheap steel elsewhere. Hot rolled coil prices hit historical lows and almost all Chinese mills made losses. Prices of key inputs like iron ore and coal plunged.

Beijing then redoubled previous efforts to limit output from domestic coal mines. That boosted seaborne trade as imports rose; Australian thermal coal prices have doubled this year. China’s steel-hungry, private real estate market boomed following monetary loosening in 2014. Domestic steel demand surged just as other countries erected tariff barriers against Chinese exports. Coking coal and iron ore prices duly jumped. Shares in Brazil’s iron ore producer Vale have doubled this year in dollar terms. London-listed Glencore, with up to a fifth of its earnings before interest, tax, depreciation and amortisation sourced from coal, has done even better. Prices for other industrial metals like copper, zinc and lead have also rallied.