Japanese investors are buying gold to store in Switzerland because of negative interest rates and fears the yen will depreciate as the government grapples with the heaviest public debt burden in the developed world, according to BullionVault Ltd., an online trading and storage company.

The number of buyers jumped 62 percent in the first six months from the second half of 2015, Atsuko Sato Whitehouse, head of Japanese markets at the London-based investment service, said this week. She didn’t provide details. The Bank of Japan has embarked on unprecedented bond buying to bolster the economy, prompting speculation the yen could plunge if stimulus efforts fail.

“Many of our Japanese customers think it’s too risky to hold gold bars at home and they want to keep them in Switzerland because they are anxious about the future of Japan,” Whitehouse said in an interview. The country’s growth has stagnated for a decade, defying fiscal and monetary stimulus which has driven up public debt to more than double the value of annual economic output.

Global investors have piled into gold in 2016 as market turbulence and low or negative interest rates increase the appeal of bullion. Prices soared about 30 percent to the highest in more than two years as assets in exchange-traded funds jumped 37 percent to more than 2,000 metric tons. The stampede increased after the U.K. voted to leave the European Union on June 23. Bullion is probably in the early stages of its next bull run, according to UBS Group AG.

Stimulus Failure

Rather than weakening, the Japanese currency has climbed in the past year because investors see it as a haven along with government bonds, silver and gold. That’s meant the price of the metal in yen has dropped 2.5 percent over that time even as bullion denominated in dollars has strengthened 17 percent to $1,357.54 an ounce.

The surging yen hasn’t stopped some commentators from predicting a collapse. Yukio Noguchi, a university professor and former Ministry of Finance official whose business books are best sellers, envisages a scenario in which a failure of the country’s economic stimulus could drive the yen to weaken beyond 300 per dollar. That compared with about 101 yen on Friday.

The Japanese investors attracted by BullionVault range from wealthy older businessmen who have experience working abroad and want to shelter their assets, to younger people and women seeking a haven because of increasing global economic and political risks, especially after the British vote to leave the EU, according to Whitehouse.

BullionVault sees similarities between the behavior of Japanese investors and their overseas peers, Whitehouse said. Most of its U.S. customers keep bullion abroad because they fret about the risk of confiscation, which happened during the Great Depression in the 1930s. Half of its British clients store their gold overseas, she said. The company says on its website that it’s the largest online investment gold service in the world.