Shanghai/London: Base metals including copper and zinc are closing out what’s been a mighty month on a bullish note after data from China showed further strength in the nation’s factories, boosting prices across the board and reinforcing optimism about the outlook for global demand.

Three-month copper rallied 1 percent to $6,836 a metric ton on the London Metal Exchange by 10:38 a.m. in London, heading for the highest close since 2014 and taking its gain this month to more than 7 percent. Nickel has rallied 15 percent in August, aluminum’s up 10 percent, and zinc’s 12 percent ahead. The six-metal LMEX Index closed at a three-year high on Tuesday.

Metals have rallied this year amid burgeoning optimism about consumption in China, as well as the impact of supply-side reforms, especially for aluminum. Stronger-than-expected U.S. GDP and employment figures are also lending support.

“The economic figures from the U.S., China and EU are all improving,” Richard Fu, head of Asia-Pacific sales at Amalgamated Metals Trading Ltd said by email. Short-term technical traders are also being drawn into the rally as prices break new highs, while bearish funds are also buying to stop out of their positions, he said.

‘Change in fortunes’

The gains, which have also been supported by a weaker dollar, have spurred banks to raise their outlooks. Macquarie Group Ltd boosted price forecasts in a note received on Thursday that highlighted a shift in investor attitudes.

“The biggest discernible change in fortunes for commodities has been a lifting in investor sentiment toward Chinese demand,” the Macquarie analysts wrote in the research note, which was dated August 29. “A weaker U.S. dollar is also contributing to nominal price gains, as investors apparently lose faith in the Trump administration’s strategies and coherence.”

China’s factory gauge strengthened again in August, according to Thursday’s figures, suggesting the economy’s resilience. The manufacturing purchasing managers index was 51.7, beating the 51.3 forecast in a Bloomberg survey of economists and topping July’s 51.4. Numbers above 50 indicate expansion.

The rapid jump in prices has prompted warnings from some that the gains may prove unsustainable. Oscar Landerretche, chairman of Codelco, the world’s biggest producer of copper, has said that the metal’s rally to the highest in almost three years could reverse in the coming months.

Miners have benefited from the advance in metals. The London-traded shares in commodities powerhouse Glencore Plc are headed for a third monthly advance in August, while Rio Tinto Group has added 6.6 percent this month, and BHP Billiton Ltd is also higher.