(Bloomberg) -- The world's a scarier place for investors these days and many are turning to gold, with the metal rallying in the first half more than in any year since 1974.

Market turmoil after a U.K. vote to leave the European Union simply adds to concerns over growth around the world, including China, that have pushed gold prices up 24% this year.

Investors piled into ETFs backed by the metal and volume on the largest futures exchange hit a record.

Prospects of a further U.S. interest-rate increase have been wound back since the populist Brexit vote, which has only added to a sense of uncertainty over U.S. elections this year.

"The macro environment remains eminently favorable for bullion," said Jonathan Butler, a precious metals strategist at Mitsubishi in London. "The question is whether those ETF flows and Comex volumes will prove sufficiently sticky to support prices in the second half."

Gold for immediate delivery was set for a second straight quarterly gain, rising 6.8% in the three months to $1,316.74 an ounce by 11:51 a.m. in London, according to Bloomberg generic pricing. It jumped to the highest in more than two years on June 24 after the Brexit vote.

Surging prices after the U.K. result deals a blow to demand in India, the second-largest consumer, and may cut imports to the lowest in seven years, according to Bachhraj Bamalwa, a director at the All India Gems & Jewellery Trade Federation.

Global investor demand remains strong.

Holdings in gold-backed ETFs rose 7.6 tons to 1,947.9 tons on Wednesday, the highest level since September 2013. They have jumped 33% this year, the biggest first-half increase since 2009. Investors traded 28.7 million futures contracts on the Comex, the busiest first quarter on record, data compiled by Bloomberg show.

In other metals:

Spot silver climbed 0.5% to $18.395 an ounce, up 19% this quarter. Palladium is headed for a 4.3% gain since March. Platinum retreated 0.4% to $1,004.89 an ounce. It's up 3% over the past three months.

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