LONDON – Platinum futures had the biggest gain in more than four months as a rise in South Africa’s rand spurred speculation that production costs would rise.

The rand led gains in emerging-market currencies as data showed South Africa’s economy expanded last quarter on a rebound in mining and factory output. The nation accounts for 73% of world platinum production, according to New York-based researcher CPM Group. Platinum has risen about 23% this year, trailing returns in silver and gold.

“It’s a perfect storm right now for platinum to trade higher,” Bob Haberkorn, a senior market strategist at RJO Futures in Chicago, said in a telephone interview. “The rand is part of the equation because that helps on the production-cost side. It also has some catching up to do.”

Platinum futures for October delivery climbed 3.8% to settle at $1 102.70/oz at 1:36 pm on the New York Mercantile Exchange, marking the biggest advance for a most-active contract since April 19.

Aggregate trading was 82% above the 100-day average for this time, according to data compiled by Bloomberg. Comex trading was shut on Monday for the Labour Day holiday.

Platinum is also benefiting from the tailwind provided to gold by the dimming prospects that the Federal Reserve will raise interest rates in their meeting this month. Traders are pricing the odds of a rate hike at 22%, down from 34% on September 1, a day before the release of US data showing US payrolls rose less than expected in July. Lower rates are a boon to precious metals because they don’t offer yields or dividends.

“Platinum has been pretty closely bound to the rand,” Grant Sporre, an analyst at Deutsche Bank AG in London, said by telephone. “A stronger local currency makes the metal more expensive to produce, so that raises expectations for future prices.”

Gold futures for December delivery advanced 2.1% to $1 354/oz on the Comex in New York, a third straight gain, the longest rally since August 2. ABN Amro Group NV’s Georgette Boele, who was a top forecaster in the second quarter, cut estimates for the metal on the subdued market reaction to the UK’s decision to leave the European Union and expectations for higher US interest rates.

Silver futures also rallied on the Comex, while palladium climbed on Nymex.