What Is the S&P 500?

What Is the S&P 500?

The S&P 500 is a market-capitalisation-weighted index that tracks the share prices of 500 large companies listed on United States stock exchanges. It is maintained by S&P Dow Jones Indices and is widely regarded as the single most representative measure of the broad US equity market. When financial professionals say "the market is up" or "the market is down", they are most often referring to the S&P 500.

For South African investors, the index matters because it underpins a large share of global equity exposure held through rand-denominated unit trusts, exchange-traded funds (ETFs), and offshore investment allowances. Understanding how it is built, what drives it, and what it does not capture is essential before allocating capital to any product that tracks it.

How the S&P 500 Is Constructed

The Index Committee and Eligibility Rules

S&P Dow Jones Indices does not simply take the 500 largest US companies by market capitalisation and call it done. An index committee applies a formal set of eligibility criteria before a company can be considered for inclusion:

• Domicile and listing: the company must be incorporated in the United States and listed on an eligible US exchange (the New York Stock Exchange or Nasdaq).
• Market capitalisation: the unadjusted market cap must meet a minimum threshold, reviewed periodically by the committee. The exact figure is published in the index methodology document and changes over time, so consult the S&P Dow Jones Indices methodology directly for the current number.
• Float-adjusted liquidity: at least 50 percent of shares must be available to public investors (the float). Tightly held companies with most shares locked up by founders or governments may not qualify.
• Financial viability: the sum of the most recent four quarters of as-reported earnings must be positive, and the most recent quarter must also be positive. This profitability screen is one reason some large but loss-making technology companies spent years outside the index.
• Minimum trading liquidity: the ratio of annual dollar value traded to float-adjusted market cap must exceed 1.0.

Once a company meets all criteria, the committee considers it for inclusion, typically when an existing constituent is removed through merger, acquisition, delisting, or a significant fall in market cap. Additions and removals are announced in advance, giving market participants time to adjust positions.

Market-Capitalisation Weighting

The S&P 500 uses float-adjusted market capitalisation weighting. Each company's weight in the index equals its float-adjusted market cap divided by the total float-adjusted market cap of all 500 constituents. This means larger companies have a proportionally greater influence on the index's daily movement.

As at the time of writing, the five largest constituents (Apple, Microsoft, Nvidia, Amazon, and Alphabet, in approximate order) collectively represent a significant double-digit percentage of the entire index. A 5 percent move in any one of these companies can shift the index noticeably, even if the other 495 constituents are flat. This concentration is a structural feature, not an anomaly, and it is something investors in passive S&P 500 trackers accept implicitly.

What the Index Does Not Include

The S&P 500 covers roughly 80 percent of available US equity market capitalisation, but it excludes:

• Mid-cap and small-cap US companies (covered by the S&P MidCap 400 and S&P SmallCap 600 respectively)
• Non-US companies, even if they are large global businesses
• Bonds, commodities, currencies, and private assets
• Companies listed on over-the-counter markets or smaller exchanges

This means the index is not a proxy for the global economy, nor for the US economy in its entirety. Many of the 500 companies generate the majority of their revenues internationally, so the index is better described as a measure of large US-listed corporate performance rather than the US domestic economy alone.

A Brief History of the S&P 500

S&P Dow Jones Indices launched the S&P 500 in its current form on 4 March 1957, expanding from an earlier 90-stock index that Standard and Poor's had maintained since 1926. The 1957 launch coincided with the early adoption of computers for financial calculation, making a 500-stock index practically manageable for the first time.

Key milestones in the index's history include:

• 1976: Vanguard launched the first index mutual fund for retail investors, tracking the S&P 500. This was the beginning of passive investing as a mainstream strategy.
• 1993: The SPDR S&P 500 ETF Trust (ticker: SPY) began trading on the American Stock Exchange, becoming the first US-listed ETF. SPY remains one of the most traded securities in the world by daily dollar volume.
• 2000 to 2002: The dot-com bust saw the index fall approximately 49 percent from peak to trough, illustrating the risk of concentration in a single sector at a moment of speculative excess.
• 2008 to 2009: The global financial crisis produced a peak-to-trough decline of approximately 57 percent, the steepest in the index's modern history.
• 2020: A pandemic-driven collapse of roughly 34 percent in 33 days was followed by one of the fastest recoveries on record.

Over the long term, the S&P 500 has delivered positive total returns (price appreciation plus dividends reinvested) in the majority of calendar years, but it has also produced extended periods of flat or negative real returns. Investors who held through the period from 2000 to 2012, for example, experienced what some analysts call a "lost decade" in nominal terms.

How the S&P 500 Is Used by Investors

As a Benchmark

Fund managers whose mandates include US or global equities are routinely measured against the S&P 500. A fund that returns 10 percent in a year when the index returns 15 percent has underperformed, regardless of the absolute gain. This benchmark function drives an enormous amount of portfolio construction behaviour.

As a Passive Investment Vehicle

Because the index is rules-based and transparent, it can be replicated mechanically. Index funds and ETFs that track the S&P 500 have accumulated trillions of dollars in assets globally. The investment case for passive tracking rests on two observations: most active managers underperform the index over long periods after fees, and index funds charge materially lower fees than active funds.

For South African investors using their annual offshore investment allowance, rand-denominated feeder funds and JSE-listed ETFs provide access to S&P 500 exposure without requiring foreign currency accounts. Products of this type are regulated by the Financial Sector Conduct Authority (FSCA) and must comply with Collective Investment Schemes Control Act requirements. Investors should review the relevant fund's minimum disclosure document (MDD) and understand the currency risk: returns are earned in US dollars but converted to rand, and rand depreciation against the dollar amplifies returns in rand terms while rand appreciation reduces them.

Within Retirement Fund Portfolios

South African retirement funds governed by Regulation 28 of the Pension Funds Act face limits on offshore exposure. As at the most recent regulatory position, the offshore allowance for retirement funds sits at 45 percent of assets, with an additional Africa allowance. S&P 500 exposure accessed through a compliant feeder fund falls within this offshore allocation. Trustees and fund administrators should confirm the current limits with their legal advisers, as Regulation 28 has been amended multiple times and the precise figures are subject to change.

Understanding S&P 500 Sectors

The index is divided into 11 sectors using the Global Industry Classification Standard (GICS), developed by MSCI and S&P Dow Jones Indices. The current 11 sectors are:

1. Information Technology
2. Health Care
3. Financials
4. Consumer Discretionary
5. Communication Services
6. Industrials
7. Consumer Staples
8. Energy
9. Utilities
10. Real Estate
11. Materials

Sector weights shift constantly as market caps change and as the committee reclassifies companies. Information Technology has been the dominant sector by weight for much of the past decade, driven by the appreciation of companies such as Apple, Microsoft, and Nvidia. This sector concentration means S&P 500 returns have been heavily influenced by technology earnings cycles and interest rate sensitivity, since high-growth technology valuations are particularly sensitive to changes in discount rates.

Investors who want to tilt toward or away from a particular sector can do so through sector-specific ETFs, though this introduces active decision-making and the associated risk of being wrong about relative sector performance.

The Difference Between Price Return and Total Return

The S&P 500 is quoted in two forms:

• Price return index: reflects only changes in share prices. This is the figure most commonly cited in news headlines.
• Total return index: adds dividends reinvested back into the index. Over long periods, dividends contribute meaningfully to compound returns. The S&P 500's dividend yield has historically ranged from under 1 percent to over 6 percent depending on market conditions.

When comparing fund performance against the index, it is important to confirm whether the benchmark being used is the price return or total return version. A fund that reinvests dividends should be compared against the total return index, not the price return index, to avoid a misleading favourable comparison.

Valuation and What It Tells You

The most widely used valuation metric for the S&P 500 is the price-to-earnings (P/E) ratio, which divides the index's price level by the aggregate earnings per share of its constituents. A related measure, the cyclically adjusted price-to-earnings ratio (CAPE, also called the Shiller P/E), uses average inflation-adjusted earnings over the prior ten years to smooth out short-term earnings volatility.

Historically, elevated CAPE readings have been associated with lower subsequent long-term returns, while low CAPE readings have preceded periods of stronger returns. However, the relationship is not precise enough to be used as a short-term market timing tool. The CAPE has remained at historically elevated levels for extended periods without an immediate correction, and it does not account for structural changes such as shifts in accounting standards, sector composition, or interest rate regimes.

For investors with long time horizons, current valuation is one input among many, not a definitive signal.

Common Misconceptions About the S&P 500

"The S&P 500 represents the US economy." It represents large US-listed companies, many of which earn most of their revenue outside the United States. The index can rise during a US recession if global demand supports corporate earnings.

"Passive investing in the S&P 500 is risk-free." The index has experienced drawdowns exceeding 50 percent. Passive investing eliminates manager risk and reduces cost, but it does not eliminate market risk.

"All S&P 500 ETFs are the same." They track the same index but differ in total expense ratio, tracking error, dividend treatment (accumulating versus distributing), currency hedging, tax treatment (particularly relevant for South African investors accessing US-domiciled funds), and the counterparty structure of the product.

"The S&P 500 is globally diversified." It is geographically concentrated in one country. Investors seeking true global diversification need exposure to non-US developed markets and emerging markets alongside any S&P 500 allocation.

Practical Considerations for South African Investors

Accessing S&P 500 exposure from South Africa involves several layers of consideration that do not apply to a US-based investor:

• Currency risk: the rand/dollar exchange rate introduces a second source of return and volatility. A rand that weakens against the dollar amplifies S&P 500 gains in rand terms; a strengthening rand does the opposite.
• Withholding tax on dividends: South African investors holding US-domiciled ETFs directly may be subject to US dividend withholding tax. The rate depends on the applicable tax treaty and the investor's structure. Rand-denominated feeder funds may handle this differently. Tax advice specific to your situation is essential.
• Exchange control: personal offshore investment allowances and retirement fund limits under Regulation 28 govern how much can be invested offshore. These limits are set by the South African Reserve Bank and the National Treasury and are subject to change.
• Product selection: JSE-listed ETFs tracking the S&P 500 are available from several local asset managers and are regulated under South African law, making them more straightforward for most retail and institutional investors than holding foreign-domiciled products directly.

Investors should consult a licensed financial adviser and, where relevant, a tax practitioner registered with SARS before making allocation decisions.

Summary

The S&P 500 is a rules-based, float-adjusted market-capitalisation-weighted index of 500 large US-listed companies. It is the most widely followed equity benchmark in the world, the basis for trillions of dollars in passive investment products, and a standard reference point for professional fund managers. For South African investors, it offers meaningful exposure to global corporate earnings growth, but it comes with currency risk, concentration risk, and regulatory considerations that require careful navigation. Understanding the index's construction, its limitations, and the specific product through which you access it is the starting point for any informed allocation decision.