Part 6 · Commodities and the global economy · Lesson 31
Copper and chip prices: the thermometer of the economy
The price of copper and the price of memory chips are thermometers that tell you in advance how busy the world's factories are. But even a thermometer sometimes runs a fever for other reasons.
QToday's question
Why are copper and DRAM prices called the 'thermometer of the economy'? And why do chip stocks so often rise when earnings are at their worst?
In 2023, SK Hynix posted an annual operating loss of KRW 7.7 trillion. Yet its stock price rose 88.7% by year-end that year. Conversely, in 2022, when semiconductor exports hit an all-time high, the stock fell 42.7%. In this lesson, we look at how to read two prices that tell you in advance how busy factories are, copper and memory chips, and why stock prices move even earlier than those.
MAPLearning map for this lesson
We build it up in three steps. At the end of each step, a 'Quick check' lets you test your understanding before moving on.
In Lesson 3, you learned about the cycle in which memory chip prices swing widely with supply and demand, and in Lesson 6 about leading indicators like the PMI that signal the economy in advance. In Lesson 26, you saw that semiconductors make up a large share of Korean exports and that KOSPI moved several months ahead of exports. This lesson ties these three together as 'economic signals read through prices'.
- STEP 1 · Basic conceptsMeasuring the economy's temperature by price
You'll be able to explain why copper and DRAM are sensitive to the economy and what the nickname means.
- STEP 2 · Understanding the principleWhen the thermometer is wrong
You'll be able to check how closely copper prices and industrial production moved together, and tell apart cases where 'other fevers' like supply, the dollar and speculation get mixed in.
- STEP 3 · Real-world applicationThe DRAM cycle and chip stocks
You'll be able to look at years when chip exports and earnings diverged from the stock price, and explain that stock prices price in the cycle in advance.
STEP 1Measuring the economy's temperature by price
Economic indicators usually come out about a month later. But commodity and component prices are set in the market every day. So prices can sometimes be the fastest economic signal.
An easy analogy · The hardware store near a construction site
If wire and nails suddenly sell well at a neighborhood hardware store and their prices rise, the owner figures, 'a lot of people must be building and fixing houses these days.' When construction slows, wire piles up and prices fall. Copper is the wire of the world economy, and memory chips are the components of the world's electronics. Looking at these two prices lets you guess how busy the world's factories are.
Why did copper become a 'doctor'?
Copper conducts electricity well and bends easily, so it is widely used in wiring, building plumbing, car motors, air conditioners and refrigerators, power generation equipment and power grids. Because its uses are so broad, copper demand grows when the global economy improves and factories and construction sites get busy, and falls when the economy cools. As you learned in Lesson 3, when demand rises, prices rise. That's how copper got the nickname , a doctor who diagnoses the economy.
The copper price fell more than 60% in half a year, from a monthly average of about $8,400 per ton in July 2008 to about $3,100 in December as the financial crisis hit. In the same period, US was also down more than 11% from a year earlier. The sudden chill in the economy showed up in copper first, and more sharply.
Memory chips are the copper of electronics
Memory chips like DRAM and NAND go into every smartphone, PC and server. They are standard components with little product differentiation, so even small changes in supply and demand move prices a lot. The industry watches both the , set with large customers on a quarterly or monthly basis, and the spot price traded in the market every day. As seen in Lesson 26, the September 2026 fixed price for DDR5 16Gb was $48.00, up 687.5% from a year earlier, pushing Korean semiconductor exports to more than double in a single month.
The two prices have different uses but share the same traits. They are sensitive to the economy, are set daily, and swing widely because supply can't expand quickly. Because of these traits, both act like the of Lesson 6, reflecting the direction of the economy in advance.
Quick checkCopper prices have been rising for several months. Read as an economic thermometer, what signal is that at first glance? Can you also think of why we shouldn't conclude right away?
STEP 2When the thermometer is wrong
A thermometer is handy, but if you take your temperature right after drinking hot tea, it reads as if you have a fever. Copper and DRAM prices can also run a 'fever' for reasons other than the economy.
Reading the economic thermometer (simplified for teaching)
The interpretation for each signal combination is a simplification for teaching compiled by Robin Invest. Real judgments require looking at other indicators and market expectations as well.
How closely did they move together over 20 years?
Copper price vs. US industrial production, year-over-year change (Jan 2006 – Jul 2026, first month of each quarter)
Tap or move over the graph to see the two numbers at that point in time.
Source: FRED PCOPPUSDM (IMF global copper price, monthly average in dollars per ton), INDPRO (US Federal Reserve industrial production index). Year-over-year changes and the correlation coefficient were calculated by Robin Invest from monthly data; the graph shows only January, April, July and October for readability. Checked 2026-10-05.
Calculated from 247 monthly data points, the correlation between copper price changes and US industrial production changes is 0.44. If copper is shifted three months earlier, it rises to 0.53. This means copper prices tended to move slightly ahead of factory output. In early 2009, copper was down more than 50% from a year earlier and industrial production was down more than 13%. In April 2021, copper was up 84% and industrial production up 17%. The big moves went in the same direction.
But 0.44 means 'fairly related', not 'moves identically'. Look at the right edge of the graph. In 2026, the copper price hit the highest on record in this data, a monthly average of about $13,550 per ton in June, up around 40% from a year earlier. Yet US industrial production rose only around 1%. Going by the thermometer alone, the economy looks boiling hot, but actual factory output wasn't anywhere near that.
Common misconceptions
- "If copper rises, the economy must be getting better?"
- Copper prices also carry fevers other than the economy. Prices rise when supply falls, as with a strike or accident at a major mine, and when the seen in Lesson 24 falls and the dollar weakens, dollar-priced commodities tend to rise. Expectations of future demand, such as for power grids and data centers, and investment money also push prices up.
- "If DRAM prices are at a record high, it's time to buy chip stocks too?"
- As STEP 3 shows, chip stocks have priced in prices and earnings in advance. In some years, the time when prices were highest was actually near the peak for the stock. The point where the 'direction changes' matters more than the level.
- "Commodity prices only matter for inflation?"
- As in Lesson 7, commodity prices move inflation, but commodities with large industrial demand, like copper and memory, also show the economy's temperature. Even the same price increase means something different depending on whether demand pulled it up or blocked supply pushed it up.
Quick checkCopper is rising sharply, yet the PMI is staying below 50. How should you read the thermometer?
STEP 3The DRAM cycle and chip stocks
Now let's look at the most Korean of thermometers, memory chips. Lining up the numbers shows how far ahead the stock price moves.
Semiconductor export growth vs. SK Hynix annual stock price change (2019–2025)
Tap a bar to see that year's export value and operating profit together.
Source: Semiconductor exports are from the Ministry of Trade, Industry and Energy and the Korea Semiconductor Industry Association (see the sources in Lesson 3); SK Hynix operating profit is from the company's earnings releases (K-IFRS consolidated); stock prices are year-end closes from Naver Finance, calculated by Robin Invest (excluding dividends). The 2025 stock price bar is shown shortened. This is a representative example to explain the sector cycle, not a recommendation to buy or sell a particular stock. Checked 2026-10-05.
In 2022, Korean semiconductor exports were $129.2 billion, an all-time high at the time, and SK Hynix posted an operating profit of KRW 7.0 trillion. Yet its stock fell 42.7%. Conversely, in 2023, exports fell nearly 24% to $98.6 billion and the company posted an operating loss of KRW 7.7 trillion, yet the stock rose 88.7%. 2019 is similar. In a year when exports fell 26% and earnings dropped sharply, the stock rose 55.5%.
The reason is the idea you learned in Lesson 20. Investors price a stock based not on this year's earnings but on next year's and the year after's. When memory prices show signs of bottoming, investors start buying the 'next boom' in advance even if the company is still losing money. When prices are at their peak, worries that 'the only way left is down' get priced in first. That's why chip stocks repeatedly rose when earnings were at their worst and fell when earnings were at their best. It is also why the P/E trap from Lesson 3 often shows up in whose earnings swing widely.
For stocks: how to use the thermometer
Generally favorable when copper and DRAM prices are rising
Semiconductors · nonferrous metals · wire and cable · industrials
When memory prices rise, chipmaker earnings tend to grow, and when copper prices rise, the selling prices of nonferrous metal smelting and wire and cable companies tend to rise. If an economic recovery comes with it, industrials such as machinery and transportation also benefit.
Cost burden can grow
Manufacturers that buy memory · industries that use a lot of copper
Smartphone, PC and server assemblers see costs rise when memory prices rise. Appliance and equipment makers that use copper as a raw material also see profit margins shrink if they can't pass the cost on to selling prices (price pass-through, Lesson 9).
| Headline example | What to look at first | Question for interpretation |
|---|---|---|
| "Copper hits record high" | PMI · industrial production | Did demand pull it up, or is it supply, the dollar or investment money? |
| "DRAM fixed price rises for a second month" | Turning point in direction | Has it just turned up from the bottom, or has it already been rising for a long time? |
| "Memory inventory rises, production cuts under review" | Inventory · utilization | Is it a sign prices are turning down, or production cuts that firm up the bottom? |
| "Chip stocks surge despite continued losses" | Next year's earnings outlook | Is the market already pricing in the next cycle? |
You can check recent sector trends on the Theme Map, and how exports and commodity factors are reflected in sector conditions on the impact map of the Macro Map. The earnings schedule for chip companies is on the Calendar.
This isn't always the case. How far stock prices run ahead of the cycle differs each time, and there are periods, like 2025–2026, when prices and stocks both rise for a long time together. One company's case is only an example showing the sector cycle, and an individual company's stock price is also heavily affected by other factors such as technological competitiveness and orders.
Quick checkNews came out that a memory company posted a loss, but its stock rose that day. What interpretations are possible?
✓What we learned today
- Copper is used across industry, in wiring, construction, cars and appliances, so its demand moves with the economy. That is how copper earned the nickname 'Dr. Copper'.
- In monthly data from 2006 to 2026, the correlation between the one-year change in copper prices and the one-year change in US industrial production was 0.44, rising to 0.53 when copper is shifted three months earlier. They tend to move together, but not perfectly.
- Besides the economy, copper prices also mix in mine supply disruptions, the value of the dollar and investment demand. There are periods, like 2026, when copper is at a record high but industrial production grows only around 1%.
- DRAM prices swing chip company earnings greatly. But chip stocks have tended to rise first when earnings are at the bottom and fall first when earnings are at the peak (2019 and 2023 vs. 2018 and 2022).
- Price signals need to be read for both 'direction' and 'the point where it changes'. More important than the fact that a level is high is the moment when a rising price turns down or a falling price stops.
If copper and chip prices are thermometers reflecting the global economy, the biggest pillar of that global economy is the US. In the next lesson, we use real data to see how the US stock market overnight spreads to KOSPI the next morning.
Quiz5-question quiz
Pick an answer and it's graded right away with an explanation.
Q1. What is the main reason copper prices are called 'Dr. Copper'?
Copper is used widely in wiring, construction, cars, appliances and even power grids. So demand rises when the economy improves and falls when it worsens, and the price acts like a doctor diagnosing the economy.
Q2. In monthly data from 2006 to 2026, the correlation between copper price changes and US industrial production changes was 0.44, and 0.53 when copper was shifted three months earlier. What is the correct interpretation?
0.44–0.53 means 'fairly related'. It fit better when copper was placed earlier, so copper prices tended to move slightly ahead of output. But it is not a perfect relationship.
Q3. The PMI is below 50, yet copper alone is rising sharply. Which of the following is not a cause to suspect first?
A PMI below 50 means factory orders are falling. If copper still rises, suspect 'other fevers' first, such as supply problems, a weaker dollar, and expectations and investment money.
Q4. In 2023, SK Hynix posted an operating loss of KRW 7.7 trillion, yet its stock rose 88.7%. How would you explain this using Lessons 1 and 20?
Stock prices move on future earnings rather than this year's (priced in). Rising expectations that memory prices were firming at the bottom pushed the stock up ahead of results. Chip exports actually fell that year.
Q5. When memory prices rise sharply, who could face a bigger cost burden?
Rising memory prices are a gain for those who make it but a cost increase for those who buy and use it. If they can't pass it on to selling prices, profit margins shrink (price pass-through, Lesson 9).
NextTerms · Next lesson · Related tools
A nickname for the copper price. Copper is used across industry, in wiring, construction, cars, appliances and power grids, so its demand moves with the economy, meaning the copper price acts like a doctor diagnosing the economy. It also moves with supply disruptions, the dollar and investment money, so it is not a perfect signal.
DRAM fixed contract priceDRAM contract priceThe DRAM supply price that memory chip companies set with large customers such as PC, server and smartphone makers on a monthly or quarterly basis. It moves later than the spot price traded daily, but it connects directly to chip company earnings.
Industrial productionIndustrial productionAn indicator that expresses as an index the output produced by industries such as mining, manufacturing and utilities. It is released monthly by the Federal Reserve in the US and Statistics Korea in Korea, and is used as a coincident indicator of the economy.
CommoditiesCommoditiesBasic materials used in production, such as crude oil, natural gas, metals and grains. When their prices rise, they push up inflation and boost the profits of companies that produce and sell them.
Price cyclePrice cycleA pattern in which supply reacts slowly to changes in demand, so prices rise too far and then fall too far, repeatedly. It is especially pronounced in memory semiconductors, chemicals and shipping.
PMIPurchasing Managers' IndexA survey index that asks corporate purchasing managers about the economy. Above 50 is read as expansion and below 50 as contraction.
Leading indicatorLeading indicatorAn indicator that moves ahead of the actual economy. Stock prices, the PMI and the term spread are typical examples.
Cyclical stockCyclical stockAn industry or stock whose earnings swing widely with the business cycle. Semiconductors, chemicals, steel, autos and shipbuilding are typical examples.
Priced inPriced inA state in which something expected to happen is already reflected in prices such as stock prices or interest rates. If things happen as expected, prices do not move much.
Operating profitOperating profitProfit from the core business: revenue minus cost of sales and selling, general and administrative expenses.
Dollar indexDollar indexThe average value of the dollar against several currencies such as the euro and yen. There is the DXY, based on six major currencies, and the Fed's broad dollar index, which covers a wider group of trading-partner currencies.
Export concentrationExport concentrationThe degree to which exports are concentrated in one or two items. The semiconductor share was about 21% in 2024 and 24.4% in 2025, and grew to about 50% by September 2026. The greater the concentration, the more that item's cycle shakes exports and the whole stock market.
This is educational material and not investment solicitation. There is no guarantee that past relationships will repeat in the future.