Arrivals of unwrought copper, including anode, refined and semi-finished copper products into China stood at 404,000 tonnes last month, the General Administration of Customs said. That was down 3.8% from 420,000 tonnes in July and also down 3.8% year-on-year.

The decline came despite copper prices in China being mostly high enough in August for traders to make a profit by buying on the London Metal Exchange, the global price benchmark, and selling on China’s Shanghai Futures Exchange, encouraging bookings of physical copper imports into China.

But factory activity in China, which is embroiled in a bruising trade war with the United States, shrank for a fourth straight month in August, according to an official survey, in a bearish sign for the manufacturing sector that is a key source of copper demand.

“While the economic data has been a little bit weak, some of the more end-use sectors (for copper) have shown signs of recovery,” said Daniel Hynes, commodities strategist at ANZ, before the data was released.

China’s imports of copper concentrate, or partially processed copper ore, came in at 1.815 million tonnes in August, down 12.5% from the previous month’s record high of 2.07 million tonnes but up 9.3% year-on-year.

“There has been a general, ongoing shift in the type of copper China has been importing,” because of expanding smelting capacity that can process concentrate, Hynes said, noting that – taking unwrought and concentrate imports together – apparent consumption of copper units had grown this year.

Meanwhile, China’s aluminium exports fell 4.3% in August from the previous month despite a weaker yuan as unexpected production outages at two key smelters meant there was less metal available for overseas shipments.

China, the world’s top aluminium producer, last month exported 466,000 tonnes of unwrought aluminium, including primary metal, alloy and semi-finished products.

The total was the lowest since February and was also down 9.9% from August 2018.