The global activity dispersion index averaged 46.5 in January, sharply lower than the 55.2 recorded in December, with 2020 activity levels said to be remarkably higher than 2019 driven by China's post-pandemic recovery.
The January drop was put down to a large decline in European activity levels and continued weakness in North America.
Europe fell from 59.9 to 41.3, taking the region back to levels similar to the first quarter of 2020.
North American activities continued to be depressed, down from 33.6 in December to 33.2, well below the September rebound figure of 56.5, suggesting pandemic-related shutdowns remained a major factor.
South America followed the downward trend, from 49.7 to 43 in January.
The China index fell from 55.5 to 50.3 in January but the country's activity remained more robust than elsewhere, Marex Spectron's global head of analytics Dr Guy Wolf said.
"The start of 2021 has been extremely soft for global smelting activities," he said.
"However, the slowdown we saw in China towards the end of January followed a period of quite intense activity, suggesting a certain amount of re-stocking had been taking place ahead of the Chinese New Year holiday season.
"The primary driver of the global weakness in January was the large decline in European activity levels and continued weakness in North America.
"Clearly, this is pandemic-related and the experience of 2020 suggests that we should expect a similarly aggressive recovery as lockdowns are lifted."
The data comes as the copper price is at nine-year highs, above US$8,400/t, amid expectations of a global economic recovery and tight supply.
The SAVANT platform monitors up to 90% of global copper smelting capacity.
Readings below 50 in the activity dispersion index indicate less activity levels than average.