Societe Generale put a number on it in a note dated August 10: roughly a 37% chance that Washington imposes a 30% duty on refined copper by January 2028.
The bank did not get there through a leak. It read the price gap between copper in New York and metal delivered against the London benchmark. When New York trades at a fat premium, traders are expecting an import tax, and because the premium can be measured, the odds can be backed out of it.
None of this is law. A White House proclamation in July 2025 floated a phased duty on refined copper, 15% from January 2027 and 30% a year later, but tied it to a Commerce Department review due by mid-2026. The refined-copper levy is still a proposal.
What is already in force
One copper tariff does bite. Since August 2025 the US has charged 50% on semi-finished copper products and copper-heavy goods under a Section 232 order. Refined cathode metal was left out of that first round, which is why the 2028 question is still open.
Chile’s exposure
Chile mines more copper than any other country, about 5.3 million tonnes in 2025 by US Geological Survey data. In the first eleven months of 2024 it sent 544,000 tonnes of cathodes worth US$5.08 billion to the US, and state-owned Codelco supplied 45% of that. A 30% rate on that flow would mean about US$1.52 billion in duty, before any change in prices or volumes.
The damage would likely be smaller than that sounds. The US takes only around 11% of Chile’s copper exports, Asia and Europe buy most of the rest, and America refines little copper itself. Exporters like Codelco could steer more cargoes to Asia. Some of the cost would land on American buyers through higher prices.
The trigger to watch is the Commerce review and whatever the president decides afterward. If a 15% duty arrives in 2027, the 2028 odds would probably jump. Until then the 37% is a reading of nerves that can swing with the headlines, not a forecast.
