The worldwide glut of copper supply is poised to almost triple in 2014, driving prices to the lowest in at least three years, at a time when the International Monetary Fund says economic growth will be weaker than forecast.

The surplus will reach a 13-year high of 272 000 t, according to data from Barclays and the International Copper Study Group. Codelco and Freeport-McMoRan Copper & Gold, the biggest producers, are among those scheduled to add supply next year. The metal will drop as low as $6 450/t in 2014.

New mines or expansions to existing pits from Mongolia to Indonesia to Chile will boost output as producers respond to prices that more than tripled in the past decade. Shortages occurred in seven of the last ten years as the Chinese economy expanded almost sixfold. Mining companies are finally catching up just as growth in China, the world’s second-largest economy and consumer of two in every five tons, is projected to be the lowest in almost a quarter century.

“We’ve got enough of a surplus to keep prices under pressure,” says Robin Bhar, an analyst at Société Générale, in London, who has covered metals for about 25 years. “You’re going to have to see demand really surprise, which I don’t see, given the economic environment, to knock those expectations seriously off course.”

Copper fell 8.8% to $7 234.25/t on the London Metal Exchange (LME) this year, tumbling into a bear market in April. The LME index of six industrial metals dropped 9.3% because of surpluses in aluminium and nickel. The Standard & Poor’s GSCI gauge of 24 commodities declined 1%, the MSCI All-Country World Index of equities gained 14% and the Bloomberg US Treasury Bond Index lost 2.6%.

Production will jump 5.1% this year and 4.9% in 2014, twice the pace in 2012, according to London-based Barclays. Growth in demand will slow to 4.1%, from 4.8% in 2013, expanding the surplus from 94 000 t. Stockpiles in warehouses monitored by bourses in London, New York and Shanghai reached 934 654 t in June, the most since 2003, according to data compiled by Bloomberg.

Barclays’s prediction for a bigger copper surplus in 2014 contrasts with its forecasts for smaller gluts in aluminium, nickel and zinc. Lead shortages will worsen and the deficit in tin will be little changed, the bank says.

Copper producers may not need to curb output any time soon because the costliest mines need about $6 600/t to break even, or almost 9% below prices now, according to data compiled by Macquarie Group.

Orders to withdraw copper from LME-tracked warehouses, known as cancelled war-rants, rose fivefold this year, indicating demand may be stronger than estimated. The orders reached a record 375 425 t in June and were last at 258 275 t, still seven times the average over the past decade, bourse data show.

Supply is regularly disrupted by everything from strikes to landslides. Freeport-McMoRan, based in Phoenix, lost about 125-million pounds (56 700 t) of output in the second quarter, after halting work at its Grasberg mine, in Indonesia, because of a tunnel collapse on May 14. Rio Tinto Group’s $6.6-billion Oyu Tolgoi project, in Mongolia, was delayed because of disagreements with government on funding.

“I’ve been to Asia recently and I see solid demand,” Javier Targhetta, the senior VP of marketing and sales at Freeport-McMoRan said in an interview in London on October 8. “I’ve seen a very solid market in China. The recovery of the US is a fact. There are promis-ing signs in Europe.”

A Chinese manufacturing index compiled by HSBC Holdings and Markit Economics reached a six-month high in September. The Chinese government’s broadest measure of credit rose more than forecast in August, signalling that a rebound is strengthening.

Faster economic growth may not be enough to spur an acceleration in the country’s refined copper imports, which rose 4.8% from a year earlier in August, according to customs data. Unwrought imports climbed 16% from a year earlier in September, reaching an 18-month high. Stockpiles held in China’s bonded warehouses, separate to those tracked by the Shanghai Futures Exchange, climbed 50 000 t to 450 000 t in August, Maike Futures Brokerage says.

That is more than the 31 500 t withdrawn from bourse-monitored depots in the past three months. Premiums that buyers pay on top of the exchange price to secure immediate supply fell in September, an indication more metal was available, according to Standard Chartered.

Codelco, owned by Chile’s government, plans to invest $4-billion to $5-billion a year in the next five years to boost output, CEO Thomas Keller said in an October 7 interview in London. The Santiago-based company’s $3-billion Mina Ministro Hales is scheduled to open later this year, eventually adding another 183 000 t to global supply.

Mina Ministro Hales and Chinalco Mining’s Toromocho mine, in Peru, will be among the ten biggest capacity additions next year, adding a combined 811 000 t of output, according to Morgan Stanley.

Freeport-McMoRan will report a 15% drop in profit to $2.59-billion this year, the mean of nine analyst estimates compiled by Bloomberg shows. Shares of the Phoenix-based company, which gets 79% of its revenue from copper, fell 2.2% to $33.44 in New York trading since the start of January. They will reach $36.94 in 12 months, according to the average of 16 analyst forecasts.

Aurubis, Europe’s largest producer of refined copper, cut its annual profit forecast on August 13, citing price swings and weaker European demand. The Hamburg-based company should be able to charge mining companies more for processing ore next year as mine output expanded, CEO Peter Willbrandt said in an interview in London on October 7. Higher returns for smelters worldwide may accelerate the surge in supply.

“As you get into the end of the year, the surplus will become more apparent,” said Gayle Berry, an analyst at Barclays, in London, who has covered metals for more than a decade. “Things are looking better from a demand perspective but [when] you look at supply, copper mine supply is growing at the fastest that it has in almost a decade.”