When the S&P 500 Rises, but You're in the Red: The Hidden Dollar Leverage in a Czech Portfolio

You're sitting in the evening with your app, checking the news: "S&P 500 closed up 1.4%." You open your broker with satisfaction — and your account is glowing red. For a moment, you think the app is malfunctioning. It's not. You've just encountered one of the most underestimated forces in a Czech investor's portfolio: the USD/CZK exchange rate.

While everyone talks about interest rates and corporate earnings, the dollar quietly works in the background. It can add or subtract a few percentage points from your returns without a single stock in your portfolio losing value. Let's break it down with numbers.

First: What DXY Actually Measures

DXY (the dollar index) is not the exchange rate against the koruna — it's a basket that measures the dollar's strength against six major currencies, with the euro playing a dominant role (over 57% weight), followed by the Japanese yen, British pound, and others. When DXY rises, the dollar is "strong" against the world. Historically, the index has moved roughly in the range of about 90–115 points; it's not a rocket, more like a slow wave that can still pull entire markets.

A good example is the year 2022. When the Fed sharply raised rates from zero to around 5%, it triggered a global chase for dollars — investors wanted to park money in U.S. bonds with suddenly attractive yields. DXY then soared from around 95 points to over 114 points, the highest level in two decades.

Why should an investor care? Because a strong dollar has two classic impacts:

1) Corporate Trap: Revenues in Euros, Reports in Dollars

American companies in the S&P 500 index make approximately 30–40% of their revenues outside the USA. Imagine a software giant selling a license in Germany for 100 EUR:

At an exchange rate of 1.20 USD per euro, it reports revenue of 120 USD after conversion.
When the dollar strengthens and the rate drops to 1.00 USD per euro (parity), the same sale represents only 100 USD in accounting.

The company in Europe didn't sell a single unit less — yet its reported revenues in dollars drop by nearly 17%. That's why during periods of a strong dollar, you often hear the phrase "foreign exchange headwinds" on conference calls — the currency headwind that cut into profit growth. And Wall Street knows how to react with a sell-off.

2) Commodity Pressure

Oil, gold, copper, wheat — they are traded globally in dollars. When the dollar strengthens, the same ounce of gold costs more in the buyer's currency outside the USA, which dampens demand. Simply put: a strong dollar and commodities often tend to move in opposite directions. It's not a hard and fast rule, but it's a relationship that repeatedly appears in the data.

Now the Important Part for a Czech: Exchange Rate Risk in Both Directions

This is where most people overlook. When you, as a Czech, buy an American stock, you're actually holding two bets at once:

a bet on the price of that stock (in dollars),
a bet on the USD/CZK exchange rate.

And they add up. Sometimes they help you, other times they fight against each other.

Numerical Example — So It's Not Just Fog

Let's say you buy an American ETF or stock for 10,000 USD. On the day of purchase, the exchange rate is 23.00 CZK per dollar. So you've invested 230,000 CZK.

After a year, this happens: the asset's price in dollars grows by a nice 10%, so you have 11,000 USD. But in the meantime, the dollar has weakened to 21.00 CZK.

Calculate the return in korunas:

Value in korunas now: 11,000 × 21.00 = 231,000 CZK
Originally: 230,000 CZK
Your actual return: +0.4%

The American investor with the same position celebrates +10%. You have practically zero. You did nothing wrong — the dollar's weakening ate up almost the entire profit.

And now the same thing in reverse. The asset's price stagnates (0%), you still have 10,000 USD. But the dollar has strengthened to 25.00 CZK:

Value in korunas: 10,000 × 25.00 = 250,000 CZK
Return: +8.7% — purely from the exchange rate, the stock didn't move.

This is the crux: the exchange rate acts as leverage in both directions. It's not just a risk "downward." It's a risk in both directions — that's why it's professionally called exchange rate risk, not exchange rate loss.

A Statistic Worth Keeping in Mind

A few reference points to put it into perspective:

The USD/CZK exchange rate over the past decade has moved roughly in a wide range of about 20–25 CZK per dollar. That's a difference of over 20% between the extreme values — enough to rewrite the annual return of an entire portfolio.
Annual fluctuations in the USD/CZK rate in the range of a few percent are common; it's not a marginal detail.
For long-term holding (10+ years), the exchange rate tends to have less relative weight — because stock returns accumulate and currency fluctuations often partially offset each other in both directions. In the short term, however, the exchange rate can completely overwhelm the result.

Important: no one can seriously tell you where the exchange rate will go next year. Anyone who claims to know for sure is selling you an illusion. The goal is not to predict the exchange rate, but to understand it and account for it.

Practical Framework: What to Do as an Investor

Here's a specific checklist you can work with today:

1) Break down your return into two parts. For each of your American positions, learn to look separately at the return in dollars and the impact of the exchange rate. Most brokers show only one number in korunas — and then you don't know if the result is due to the company or the exchange rate. Breaking it down gives you clarity on what's actually working.

2) Clarify your entire portfolio's currency exposure. Add up how much of your assets are effectively in dollars. If it's a large portion, you're more dependent on the exchange rate than you thought. There's nothing wrong with that — just be aware of it.

3) Consider currency diversification consciously. There are also euro or currency-hedged (CZK-hedged) ETF variants where exchange rate risk is mitigated for a small fee (its amount is related to the interest rate difference between CZK and USD). This is especially useful for more conservative, bond investments where currency fluctuations could easily wipe out the entire return. It's not "better" or "worse" — it's a different risk profile. The decision is up to you and your horizon, this text doesn't tell you what to buy.

4) Stop panicking over daily fluctuations. When you see "S&P is rising and I'm in the red," the first step is to check the exchange rate, not sell. Nine times out of ten, the explanation is right there.

5) Average instead of predicting. By regularly investing (DCA) at monthly intervals, you average not only the purchase price of stocks but also the purchase exchange rate USD/CZK. Sometimes you buy a dollar for 24 CZK, other times for 21 CZK — in the long run, the price settles at an average, and extreme fluctuations are smoothed out.

In QMA: Keep Currency Under Control, Not in the Fog

Figuring out how sensitive a specific title is to currency movements requires understanding where the company's revenues actually come from. That's why in QMA's Opportunity Comet, you get context with your selection that helps you see where the return is coming from — whether it's the company itself and its ability to withstand currency fluctuations thanks to a strong market position, or just a currency wave. Instead of reading hundreds of pages of annual reports, you have the health and fundamental strength of companies clearly in one place. QMA doesn't decide for you — it gives you data clearly so you can make decisions with open eyes.

Takeaways

The dollar is not a boring item on the edge of the news — it's a silent lever that rewrites your returns in both directions. Specifically:

Break down your return into two numbers — how much the stock made in dollars and how much the USD/CZK exchange rate added/subtracted. Without this breakdown, you're just guessing.
Find out your total dollar exposure and have it as a conscious decision, not a coincidence.
Look at the exchange rate before panicking — red numbers after a green day on Wall Street often have only one explanation.
Don't rely on exchange rate forecasts — plan so that no direction catches you off guard; take regular investing and a longer horizon as allies.

The strength of the currency can be understood, even if it can't be predicted. And understanding is exactly what distinguishes an investor from someone who just looks confusedly at red numbers.

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This article is for informational purposes only and does not constitute investment advice. Always conduct your own research or consult a financial advisor before making investment decisions.

🌍When the S&P 500 Rises, but Your Account Falls: The Role of the Dollar Exchange Rate

When the S&P 500 Rises, but You're in the Red: The Hidden Dollar Leverage in a Czech Portfolio

First: What DXY Actually Measures

1) Corporate Trap: Revenues in Euros, Reports in Dollars

2) Commodity Pressure

Now the Important Part for a Czech: Exchange Rate Risk in Both Directions

Want to know more? Ask the QMA Research Assistant

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Numerical Example — So It's Not Just Fog

A Statistic Worth Keeping in Mind

Practical Framework: What to Do as an Investor

In QMA: Keep Currency Under Control, Not in the Fog

Takeaways