Copper Fell With the S&P 500 on 87% of Its Worst Days

Copper fell on 90 of the 104 days when the S&P 500 dropped more than 2%, according to a study by SignalPilotLabs covering 2010 to 2025. That is 87% of the stock market's worst sessions. The finding challenges a common assumption that commodities diversify an equity portfolio when equities sell off.

The analysis used TradingView's daily closes for copper futures (COMEX HG1!, the front month) and the S&P 500, on days when both markets traded. Copper closes roughly an hour after the S&P 500. The study period produced 3,036 usable trading days after a filtering step designed to remove noise from the futures market's mechanics.

How the study was built

The front-month copper contract rolls to the next contract a few times each year. A trading day that straddles a switch carries the price gap between two contracts, which distorts the daily move. SignalPilotLabs therefore excluded the last four weekdays of every month and the first weekday of the following month, for both markets. That left the 3,036 days used in the headline results.

What the numbers show

The two markets moved in the same direction on 61.3% of all days studied, against the 50% a random pairing would produce. Every one of the 16 years came in above half: the lowest was 2014 at 51.3%, the highest was 2021 at 66.7%. Their correlation measured 0.31, on a scale where 1 means the two always move together and 0 means no link at all.

The relationship tightens on extreme days. Of the S&P 500's 104 drops greater than 2%, copper fell on 90. Of the index's 73 rises greater than 2%, copper rose on 56 — 77%.

Is the pattern luck?

The data splits cleanly across time. The first half of the sample, 2010 to 2017, shows 62.1% same-direction days. The second half, since 2018, shows 60.4%. The pattern holds on both sides of the sample.

SignalPilotLabs also ran a permutation test. The firm shifted copper's daily series against the S&P 500's in 2,997 different ways, which preserves each market's own behavior but breaks the pairing between them. The result: no shifted pairing came close to the real figure. The highest shifted match rate was 53.3%, well below the observed 61.3%.

The researchers then ran a robustness check on the days they had excluded. With every trading day included, the same-direction share was 60.5% — close to the headline number, confirming the filter did not manufacture the pattern.

What it means for portfolios

The study's conclusion is blunt: on the stock market's worst days, copper did not hedge. It fell too, almost nine times in ten. Held together, copper and equities behaved partly as one bet rather than two separate ones.

That matters for anyone using commodity exposure to offset equity risk. A 0.31 correlation offers some diversification on ordinary days. On the days when diversification is most needed — 2%-plus equity drops — the correlation effectively collapses toward lockstep.

The original chart shows copper's daily candles for 2025 with the S&P 500 overlaid in blue on a separate left-hand scale. Below the candles, a grid sorts the S&P's 104 big drops and 73 big rises by copper's direction, with orange squares marking matching days and grey squares marking divergent ones. Purple marks flag TradingView's contract switches.

What the data cannot tell you

SignalPilotLabs flags the limits clearly: the study says nothing about which market will move next, and nothing about whether one leads the other. It is past data. As the authors put it, the work offers "observations, not recommendations." For allocators, the practical takeaway is narrower: copper has traded as an equity amplifier in sell-offs, not a shelter, and any hedging case for the metal must rest on something other than its 2010-2025 track record.