The S&P 500 is rising, but not every stock is winning

On October 6, 2026, the S&P 500 closed at 7,818.93 points, setting a new record. Yet that number does not tell the whole story. Some companies are lagging behind while a relatively small group of large technology businesses increasingly shapes the market's direction.

That distinction matters if you invest in US shares through a fund or ETF. You may see a record in the headlines, but your own return also depends on what your investment holds, the dollar's exchange rate and the fees you pay.

The S&P 500 can rise without every stock gaining

The S&P 500 tracks around 500 large US listed companies. It is widely used as a gauge of the American stock market and covers approximately 80 percent of available US market capitalisation.

The index is weighted by market capitalisation. In other words, a company with a larger stock market value has more influence on the index than a smaller company. The index contains more stocks than companies because some businesses have multiple share classes.

Here is the first important distinction. A rising index does not mean the average company is rising at the same pace. Gains among a handful of very large businesses can outweigh losses elsewhere.

On October 6, 2026, the index closed at 7,818.93 points, up about 0.6 percent on the day. It was a record, but not proof that the entire US stock market was equally healthy. The differences beneath the headline matter.

Technology is increasingly driving the result

Technology has been a major force behind the record, alongside companies classified under communication services. These include businesses that make chips, provide cloud infrastructure or develop artificial intelligence.

The economic driver is straightforward. Companies are investing in data centres, specialised chips and computing power. Investors try to estimate how much profit those investments may eventually generate. When expectations rise, share prices can rise too.

But the concentration is substantial. According to S&P Dow Jones Indices sector data, information technology accounted for 37.9 percent of the index as of August 31, 2026. The ten largest stocks together represented 37.8 percent.

Imagine investing €10,000 in a fund tracking the index. If the ten largest positions account for around 37.8 percent, they represent approximately €3,780 of your investment exposure. That money is not held in a separate pot, but the calculation shows how much influence those companies can have on your overall result.

This works in both directions. When large technology companies rise, they can lift the index. If their earnings expectations disappoint, they can also pull it lower.

A record can coexist with losing sectors

The US stock market reached new highs in October, but not every sector benefited. On October 8, 2026, the S&P 500 fell 0.47 percent, according to Reuters. The Nasdaq lost 1.25 percent as chipmakers came under pressure. Energy stocks, meanwhile, benefited from higher oil prices.

That is why a single market index can give an incomplete picture. It tells you what a weighted collection of stocks is doing. It does not automatically tell you how many individual companies are rising or falling.

There are also major differences within technology. A company spending heavily on new data centres faces different costs and risks from a software business already selling products at scale. Both may benefit from enthusiasm about artificial intelligence, but their earnings do not have to develop in the same way.

The biggest loser also depends on the trading day and the period being measured. On October 8, technology shares were weak while energy benefited from oil prices. It would therefore be misleading to name one sector as the biggest loser without specifying a timeframe.

Your return also depends on when you invested

A record sounds positive, but it says little about the return earned by someone who invested earlier. Your result depends on your purchase price, any dividends, fund fees and the exchange rate.

Consider a simple example. You invest €10,000 in a fund tracking the S&P 500. If your investment then falls by 10 percent, you have €9,000 left. To get back to €10,000, it must subsequently rise by 11.11 percent. An equal percentage loss and gain do not cancel each other out.

There is another factor for investors in the Netherlands and Belgium. The S&P 500 is calculated in US dollars. If your fund does not hedge currency exposure, movements between the euro and the dollar affect your return in euros. US shares can rise while your euro return is lower.

Dividends matter too. A price return index measures share price changes, while a total return index also incorporates dividends according to the index methodology. Check which measure is being used before comparing performance figures.

Tax depends on where you live

In the Netherlands, investments held by private individuals generally fall under Box 3, depending on their personal circumstances and the applicable law. The calculation depends on the rules for the relevant tax year and the treatment of assets and returns. Check the Dutch Tax Administration's official information for 2026.

Belgium has a different tax system. Treatment can depend on the type of income, the circumstances in which you invest and the rules applicable to the tax year. Do not assume that a Dutch tax calculation also applies to a Belgian taxpayer. Consult official Belgian government information or a qualified tax professional.

What you ultimately keep also depends on the tax you pay. That varies by country and personal circumstances.

Ask these questions before treating a record as good news

A high index level is only one data point. Consider concentration, costs and the period over which you are investing.

Questions to ask:

1. How much of my investment depends on the largest technology companies?
2. Does my fund track a price index or an index that includes dividends?
3. What annual fund fees do I pay, and how much could they add up to over several years?
4. How would a change in the dollar affect my return in euros?
5. Which tax rules apply to my country of tax residence for the 2026 tax year?

A record does not guarantee further gains, nor does it automatically mean the market must fall. It means the weighted market value of the included stocks has reached a new high. How that gain is distributed matters just as much.

Sources

• S&P Dow Jones Indices, S&P 500 index data and sector weights
• Associated Press, How major US stock indexes fared Tuesday 10/6/2026, October 6, 2026
• Reuters, S&P 500, Nasdaq end lower as crude prices jump, chip stocks weigh, October 8, 2026
• U.S. Securities and Exchange Commission, Investor.gov, Introduction to Investing
• Dutch Tax Administration, Box 3
• Belgian Federal Public Service Finance, official tax information

This article is for educational purposes only and does not constitute financial advice.