Inventory news turned more bullish almost ten weeks before cash copper moved into a sustained premium over three-month metal.
LONDON, 8 October 2026 – Copper inventory sentiment pointed to growing availability concerns almost ten weeks before the market returned to sustained backwardation in July, according to new research from market intelligence provider Permutable.
The analysis shows that Permutable’s copper inventory sentiment measure crossed above its trailing-year norm on 13 May 2026, while London Metal Exchange (LME) warehouse stocks remained close to their April peak and cash copper traded at a $43-a-tonne discount to three-month metal.
The curve returned to sustained backwardation on 20 July. Backwardation occurs when metal for immediate delivery commands a premium over later delivery, a condition commonly associated with tighter prompt availability.
By mid-August, LME stocks had fallen to approximately 205,000 tonnes, down 49% from their April peak of 403,000 tonnes. The cash premium averaged approximately $198 a tonne in August and reached $535 on 17 August.
The sequence indicates that changing inventory news provided an early reading of developing pressure while visible warehouse holdings remained substantial.
A recurring relationship with warehouse movements
The research also examined the relationship between inventory sentiment and physical stocks over a longer period. Since January 2024, weekly inventory sentiment has shown a correlation of -0.64 with four-week changes in LME stocks. Annual sample correlations ranged from -0.51 to -0.78, with more bullish inventory coverage associated with larger stock draws.
These correlations establish an association, rather than causation or a proven forecasting lead. The almost ten-week interval refers specifically to the May-July 2026 episode.
Supply concerns remain elevated as copper enters Q4
Permutable’s analysis also tracks how the news supporting copper changed through the rally. Stronger demand sentiment emerged in April and May, followed by persistently bullish disruption coverage from June.
From June onwards, disruption sentiment exceeded one standard deviation above its trailing-year norm on 89% of days. Six of the nine thematic sentiment series were above their respective one-year norms in the latest snapshot, while rates and currency coverage provided counterweights.
The physical market has nevertheless eased from August’s most acute conditions. By 5 October, LME stocks had recovered to 244,900 tonnes and the cash premium stood at $64 a tonne, substantially below its August peak.
The findings underline the value of reading news sentiment alongside warehouse movements and nearby spreads when assessing copper availability.
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