Copper Tariff Arbitrage Reshapes COMEX-LME Spread, Says Societe Generale

Tariff-driven arbitrage is fundamentally reshaping the spread between COMEX and LME copper prices, according to a recent analysis by Societe Generale. The bank’s report, published this week, highlights how import tariffs in the United States have created a persistent price gap between the two major copper benchmarks, altering trading strategies and physical metal flows.

What is driving the COMEX-LME spread?

The spread between COMEX and LME copper futures has historically reflected logistics, financing, and regional supply-demand balances. However, Societe Generale notes that the introduction of tariffs on copper imports into the U.S. has introduced a new, dominant variable. As of early 2025, the U.S. has imposed a 25% tariff on copper imports under Section 232, which has made COMEX copper more expensive relative to LME copper. This tariff premium has become a key driver of the spread, encouraging traders to arbitrage the difference by shipping metal into the U.S. to capture the higher price.

The bank’s analysis indicates that this arbitrage is not just a short-term phenomenon but is likely to persist as long as tariffs remain in place. The spread has widened significantly since the tariff announcement, and Societe Generale expects it to remain elevated, reflecting the structural change in the market.

How are traders responding?

Traders have responded by increasing imports of copper into the U.S., with shipments from major producers such as Chile and Peru rising. This has led to a buildup of inventories in COMEX warehouses, while LME inventories have seen corresponding drawdowns. The arbitrage opportunity has also spurred new trading strategies, with some firms using spread trades to profit from the price differential.

Societe Generale points out that the arbitrage is not without risk. Logistics bottlenecks, shipping delays, and changes in tariff policy can quickly erode the profitability of such trades. Moreover, the spread’s volatility has increased, making it a more complex environment for market participants.

Implications for the copper market

The reshaped spread has broader implications for the copper market. It has altered the pricing signals that guide investment decisions in mining and refining. For U.S. buyers, the tariff means higher costs for imported copper, which could impact industries reliant on the metal, such as construction and electronics. Globally, the divergence between COMEX and LME prices may lead to a more fragmented market, with regional prices reflecting local policy rather than global fundamentals.

What should market participants watch?

Market participants should monitor U.S. trade policy closely, as any changes to tariffs could rapidly alter the spread. Additionally, the pace of U.S. inventory builds and global supply disruptions will be key factors. Societe Generale’s report suggests that the current dynamics are likely to persist, but it advises caution given the potential for policy shifts.

Conclusion

Societe Generale’s analysis underscores that tariff-driven arbitrage has become a defining feature of the copper market, reshaping the COMEX-LME spread and influencing trading and physical flows. As tariffs remain in place, this trend is expected to continue, presenting both opportunities and risks for traders and end-users alike.

FAQs

Q1: What is the COMEX-LME spread?
The COMEX-LME spread is the price difference between copper futures traded on the COMEX exchange in New York and those on the London Metal Exchange (LME). It reflects regional supply-demand dynamics, logistics, and now, tariff policies.

Q2: How do tariffs affect the copper market?
Tariffs, such as the U.S. Section 232 tariff on copper imports, increase the cost of foreign copper in the U.S. market, making COMEX prices higher relative to LME prices. This creates an arbitrage opportunity for traders to profit by shipping metal into the U.S.

Q3: Will the spread remain elevated?
According to Societe Generale, the spread is likely to remain elevated as long as tariffs are in place. However, changes in trade policy or supply disruptions could alter the current dynamics.