Copper has been on a record-breaking tear in the past year, driven largely by tariff-related trade flows. Bullish investors are betting that flatlining mine supply will drive prices even higher. A string of disappointing results is undermining expectations that global mine supply would post at least modest growth this year.

International Copper Study Group data show output fell 1.1% in the first half, with major producers Codelco and Freeport-McMoRan Inc. posting double-digit declines. Morgan Stanley, which entered the year expecting mine supply to expand, now sees it little changed or slightly lower, raising the prospect of the first annual decline since 2017. The Codelco Chuquicamata open pit copper mine near Calama, Chile, faces ongoing setbacks contributing to the supply crunch.