Swiss Gold Trading Takes Spotlight in Trade Talks With Trump

The trade imbalances that prompted President Donald Trump to slap hefty levies on Swiss imports have been driven by a small industry at the center of the world’s gold market.

The country is the world’s biggest gold-refining hub, thanks to a longstanding reputation for quality and discretion. Billions of dollars worth of gold is constantly flowing into and out of the nation, from mines in South America and Africa to banks in London and New York.

Flows of the precious metal cause big swings in the country’s trade balances, even if the Swiss refiners capture only a small portion of ...