S&P 500 ETF Investing: The Simplest Path to Market Returns

If there is one investment strategy that financial experts across the entire ideological spectrum agree on for ordinary investors, it is this: invest in a low-cost S&P 500 index fund and hold it for the long term. Warren Buffett has publicly recommended it for the non-professional investor. Jack Bogle built Vanguard around it. Nobel Prize-winning economists have endorsed it. The reason for this rare consensus is simple: the S&P 500 has delivered approximately 10% average annual returns over the past century, and the data consistently shows that paying minimal fees to own it passively outperforms most active strategies over time.

This guide explains what the S&P 500 is, how S&P 500 ETFs work, which funds are the best choices, what historical returns look like, and how to use an S&P 500 ETF as the foundation of a complete investment portfolio.

Table of Contents

1. What Is the S&P 500?
2. How S&P 500 ETFs Work
3. Historical Returns and What to Expect
4. The Best S&P 500 ETFs Compared
5. VOO vs. IVV vs. SPY: Which Should You Buy?
6. Building a Complete Portfolio with an S&P 500 ETF
7. How to Buy Your First S&P 500 ETF

What Is the S&P 500?

The S&P 500 — formally the Standard & Poor's 500 — is a stock market index that tracks 500 of the largest publicly traded companies in the United States, selected and maintained by S&P Dow Jones Indices. The index was created in 1957 and has become the most widely followed benchmark for the overall U.S. stock market.

Companies are included in the S&P 500 based on their market capitalization (total stock market value), liquidity, and financial viability as assessed by S&P's Index Committee. To qualify, a company must have a market cap above $14.5 billion (as of 2024), be headquartered in the U.S., have positive as-reported earnings over the most recent quarter and the most recent four quarters combined, and have sufficient share liquidity.

The S&P 500 is market-cap weighted: companies with larger market values represent larger portions of the index. In mid-2024, the top five companies — Apple, Microsoft, Nvidia, Alphabet (Google), and Amazon — together represent approximately 25% of the entire index. This concentration in mega-cap technology companies means the index's performance is significantly influenced by the performance of just a handful of companies.

The 500 companies in the index cover 11 sectors of the economy: Information Technology, Healthcare, Financials, Consumer Discretionary, Communication Services, Industrials, Consumer Staples, Energy, Utilities, Real Estate, and Materials. This broad sector coverage gives the S&P 500 meaningful economic diversification — though it is entirely U.S.-focused and excludes the 40% of global market capitalization outside America.

Despite covering only 500 companies out of roughly 5,000 publicly traded U.S. stocks, the S&P 500 represents approximately 80% of the total U.S. stock market's capitalization. This is why S&P 500 performance is treated as a reasonable proxy for the entire U.S. equity market.

How S&P 500 ETFs Work

An S&P 500 ETF is a fund that tracks the S&P 500 index by holding all 500 stocks in the same proportions as the index. When you buy a share of an S&P 500 ETF, you are buying a fractional stake in a fund that owns all 500 companies — providing instant diversification across the entire large-cap U.S. equity market.

S&P 500 ETFs use full replication: they hold every stock in the index at its index weight. When the index rebalances — a company is added, removed, or changes weight — the ETF automatically adjusts its holdings to match. You never need to manage any of this; the fund handles all rebalancing automatically.

ETFs trade on stock exchanges like individual shares throughout the market day. You buy and sell at the prevailing market price through your brokerage account. This intraday liquidity is a structural advantage over traditional mutual funds, which only price once per day after market close — though for long-term buy-and-hold investors, this distinction matters very little in practice.

The fund earns the same dividends the underlying 500 companies pay. Most ETFs distribute these dividends quarterly to shareholders. At Vanguard, you can opt to receive dividends as cash or automatically reinvest them in additional ETF shares — the latter is the better choice for most long-term investors, as it compounds returns through additional share accumulation.

The cost of owning an S&P 500 ETF is expressed as the expense ratio: the annual percentage fee charged by the fund manager. The best S&P 500 ETFs charge just 0.03% — meaning you pay $0.30 per year for every $1,000 invested. This near-zero cost is the primary reason index ETFs consistently outperform the vast majority of actively managed funds, which charge 10–50x more.

Historical Returns and What to Expect

The S&P 500's long-term track record is one of the most compelling in finance. Since 1957 (when the index was formalized at 500 stocks), the S&P 500 has returned an average of approximately 10.5% per year in nominal terms — roughly 7% after adjusting for inflation. This means a dollar invested in the S&P 500 in 1957 grew to over $1,000 in real purchasing power by 2024, adjusted for inflation.

However, this average return masks significant year-to-year variability:

• The S&P 500 has returned 20%+ in roughly one-third of all calendar years
• It has fallen 20% or more (bear market) approximately every 4–5 years on average
• The worst single-year return was -38.5% in 2008
• The best single-year return was +52.6% in 1954
• Over any 20-year rolling period since 1926, the market has never produced a negative real return

For an investor with a 20–30 year time horizon, the year-to-year volatility is largely irrelevant — what matters is the long-term compounding. $10,000 invested in the S&P 500 in 1994 and held for 30 years grew to approximately $200,000 by 2024, despite living through the dot-com crash, 9/11, the 2008 financial crisis, the 2020 COVID crash, and the 2022 bear market.

Past returns do not guarantee future results. However, the economic engine driving S&P 500 returns — U.S. corporate earnings growth driven by productivity, innovation, population growth, and the dollar's reserve currency status — provides structural tailwinds unlikely to vanish. Most financial planners use 7% as a conservative long-term real return assumption for S&P 500 planning purposes.

The Best S&P 500 ETFs Compared

Several issuers offer S&P 500 ETFs, but a small number stand out as optimal for most investors based on cost, liquidity, and track record:

All five track the same index (S&P 500) and deliver essentially identical pre-fee returns. The primary differentiators are expense ratio, AUM/liquidity, and structure (ETF vs. mutual fund).

VOO vs. IVV vs. SPY: Which Should You Buy?

The three most widely held S&P 500 ETFs are VOO (Vanguard), IVV (BlackRock iShares), and SPY (State Street). Here is an honest comparison:

VOO (Vanguard S&P 500 ETF)

VOO at 0.03% is the choice of most long-term buy-and-hold investors for straightforward reasons: it is managed by Vanguard, the firm literally built around the index fund concept and uniquely owned by its own fund shareholders (no external corporate profit-taking), and its expense ratio is tied for the lowest among the major S&P 500 ETFs. For investors using Vanguard accounts, VOO is the natural default. For investors at other brokers, VOO is typically available commission-free.

IVV (iShares Core S&P 500 ETF)

IVV at 0.03% is functionally identical to VOO in terms of index tracking and cost. Managed by BlackRock, the world's largest asset manager, IVV has slightly different mechanics in dividend timing and share creation/redemption but produces essentially the same total return as VOO over any extended period. IVV is the preferred choice for investors at TD Ameritrade, Schwab, or brokerages where IVV is more accessible than VOO. Either fund is an equally excellent long-term holding.

SPY (SPDR S&P 500 ETF Trust)

SPY at 0.09% is the world's most liquid ETF and the oldest (launched January 1993). Its extraordinary liquidity — daily trading volumes exceeding $20 billion — makes it the dominant choice for institutional traders, options players, and anyone executing very large trades where bid-ask spreads matter enormously. For long-term buy-and-hold investors, however, SPY's 0.09% expense ratio is three times higher than VOO and IVV for identical performance. On a $500,000 portfolio held 30 years, that 0.06% difference costs approximately $100,000 in foregone compound growth. SPY is best for traders; VOO and IVV are best for investors.

SPLG (SPDR Portfolio S&P 500 ETF)

SPLG, also from State Street, charges just 0.02% — the cheapest S&P 500 ETF available. It has grown substantially in assets but remains far less liquid than VOO, IVV, and SPY. For large institutional investments or long-term holders who trade rarely, SPLG's slightly lower cost is a genuine (if marginal) advantage. For most individual investors, the 0.01% difference from VOO amounts to $1 per year per $10,000 invested — truly negligible.

Building a Complete Portfolio with an S&P 500 ETF

An S&P 500 ETF can serve as the entire equity portfolio for many investors, particularly those who prefer simplicity. However, it does have meaningful limitations as a stand-alone holding that more comprehensive portfolio constructions address:

Limitation 1 — No small or mid-cap exposure: The S&P 500 covers only large-cap U.S. stocks. Small and mid-cap companies — which have historically delivered slightly higher long-term returns in exchange for higher volatility — are excluded. A total U.S. market fund (VTI) captures this additional exposure while still being dominated by the same large-cap companies.

Limitation 2 — No international exposure: The S&P 500 is entirely U.S.-focused. The U.S. makes up approximately 60% of global market capitalization — an S&P 500-only investor misses the other 40%. Adding VXUS (international stocks) provides global diversification and reduces the risk of extended U.S. underperformance relative to global markets (as occurred in the 2000s).

Limitation 3 — No bond exposure: For investors closer to retirement or with lower risk tolerance, adding bonds (BND) provides portfolio stabilization and reduces drawdown severity during equity bear markets.

Three practical portfolio constructions based on an S&P 500 ETF core:

One-fund portfolio: 100% VOO or IVV. Ideal for investors in their 20s–30s with long time horizons who want maximum simplicity and growth. The S&P 500's diversification across 500 large-cap companies is sufficient for most long-term investors who can tolerate volatility.

Two-fund global portfolio: 70% VOO + 30% VXUS (international stocks). Adds global market exposure while maintaining a U.S.-heavy core. This is the approach recommended for investors who want diversification beyond U.S. borders without adding bond complexity.

Three-fund classic portfolio: 55% VOO + 20% VXUS + 25% BND (bonds). The complete global stock and bond market in three funds. Adjust the stock/bond split based on age and risk tolerance — more stocks when young and far from retirement, more bonds as you approach it.

How to Buy Your First S&P 500 ETF

1. Open a brokerage account. Fidelity, Charles Schwab, and Vanguard are the top choices. All three offer $0 commissions on ETF trades and $0 account minimums. If you prefer a Roth IRA (recommended for most investors under 50), select that account type when opening.
2. Fund the account. Link a checking account and transfer your initial investment. You can start with as little as $1 at brokers that support fractional shares.
3. Place a trade. Search for the ETF ticker (VOO, IVV, or SPLG), select the number of shares or dollar amount (if fractional shares are supported), and place a market order during exchange hours (9:30 AM – 4:00 PM ET weekdays). Your shares will settle in one to two business days.
4. Enable dividend reinvestment. In your account settings, enable automatic dividend reinvestment (DRIP) so dividend payments are automatically used to buy additional ETF shares. This compounds your returns without any ongoing effort.
5. Set up automatic monthly contributions. Go to your account's automatic investment settings and schedule a recurring purchase of your chosen ETF — say, $200 or $500 per month — on payday. This automates dollar-cost averaging and ensures you invest consistently regardless of market conditions.
6. Ignore the short-term noise. Log into your account quarterly to confirm your automatic contributions are running. Otherwise, resist the urge to check daily or react to market movements. Every successful long-term S&P 500 investor's most valuable trait is patience — the ability to hold through inevitable volatility without selling.

The S&P 500 ETF is not the most exciting investment in the world. It will never generate a story about picking a stock that tripled overnight. What it will do, reliably, is compound your money at rates that historically have beaten the vast majority of professional money managers over long periods — at a cost so low it is nearly imperceptible. That combination of proven performance, near-zero cost, and effortless diversification is precisely why it has become the default recommendation of financial professionals for ordinary American investors.