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S&P 500: what the index contains and why it sits at the heart of portfolios

6 min readCompound

Key takeaways

S&P 500 is the world's most-watched equity index and the natural core of most passive investors' portfolios. But what exactly does it contain?

What the index contains

The index groups roughly 500 of the largest US companies across sectors — technology, healthcare, financials, consumer goods, industrials. It is not mechanically the "500 biggest"; a committee decides inclusion based on rules covering size, liquidity and earnings history. Together, the index covers around 80 % of the value of the US equity market.

How it is weighted

S&P 500 is weighted by market capitalisation — the bigger the company, the larger its share. The consequence: several of the largest technology firms (Apple, Microsoft, NVIDIA, Alphabet, Amazon and others) together make up a large portion of the index. That is both a strength (you let winners grow) and a risk (concentration at the top).

What returns and risks it carries

Over the long run, S&P 500 has returned roughly 7–10 % per year nominally (with dividends reinvested), but the journey was far from smooth — the index repeatedly fell 30–50 % and then recovered. In the short term it is a bumpy ride; over the long term it is an engine of growth.

Watch out for concentration: the weight of a few giants is historically high today. It is still 500 companies, but the result is driven mainly by the top tier. Anyone wanting to spread the risk more broadly can look at a global index.

How to buy it from the Czech Republic

American ETFs (SPY, VOO) cannot be bought in the EU; instead you use their Irish UCITS equivalents: CSPX (accumulating, tax-efficient for growth) or VUSA (distributing, pays a dividend). Both have very low fees. You can find them in the ETF overview; a separate article explains why the Irish domicile matters.

FAQ

How many companies are in S&P 500?

Roughly 500 of the largest US companies. The exact composition changes continuously according to the index rules and committee decisions.

What is the long-term return of S&P 500?

Historically roughly 7–10 % per year nominally with dividends reinvested, but with large swings. Past returns do not guarantee future results.

How can I buy S&P 500 from the Czech Republic?

Through Irish UCITS ETFs such as CSPX (accumulating) or VUSA (distributing) via a standard broker.

Is S&P 500 sufficiently diversified?

It covers 500 companies, but today it is concentrated in a few giants. Anyone wanting broader diversification can add a global index.

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