If you’ve spent any time reading about investing or watching financial news, you’ve heard this phrase over and over:
“The S&P 500 is up today.” “The market dropped 2% — the S&P 500 fell sharply.” “Just invest in the S&P 500 and forget about it.”
But what actually is the S&P 500? Why does everyone treat it like the be-all and end-all of investing? And how do you actually invest in it?
Let’s break it down.
What is the S&P 500?
The S&P 500 is a stock market index — a list of 500 of the largest publicly traded companies in the United States, weighted by their market value.
“S&P” stands for Standard & Poor’s, the financial company that created and maintains the index. The “500” refers to the approximately 500 companies included.
Think of the S&P 500 as a report card for the U.S. economy. When the S&P 500 goes up, it means the largest American companies are collectively doing well. When it goes down, it signals that the market — and often the broader economy — is struggling.
How Did the S&P 500 Start?
The S&P 500 was officially launched on March 4, 1957, by Standard & Poor’s. However, its roots go back to 1923, when S&P first began tracking a small group of U.S. stocks.
Before the S&P 500 existed, investors mostly followed the Dow Jones Industrial Average (DJIA) — an index of just 30 large companies, created in 1896. But 30 companies wasn’t nearly enough to represent the entire U.S. stock market.
The S&P 500 was designed to give a much broader, more accurate picture of market performance — and it quickly became the standard benchmark that investors, economists, and financial professionals use to measure the health of the U.S. stock market.
Which Companies Are in the S&P 500?
To be included in the S&P 500, a company must meet several criteria:
- Be a U.S.-based public company
- Have a market capitalization of at least $18 billion
- Be profitable over the most recent quarter and the trailing 12 months
- Have its shares readily available for public trading
As of 2025, some of the largest companies in the S&P 500 include:
| Company | Ticker | Sector |
|---|---|---|
| Apple | AAPL | Technology |
| Microsoft | MSFT | Technology |
| NVIDIA | NVDA | Technology |
| Amazon | AMZN | Consumer/Tech |
| Alphabet (Google) | GOOGL | Technology |
| Meta (Facebook) | META | Technology |
| Berkshire Hathaway | BRK.B | Financials |
| JPMorgan Chase | JPM | Financials |
| Eli Lilly | LLY | Healthcare |
| Visa | V | Financials |
The index is market-cap weighted, meaning larger companies have a bigger influence on the index’s movement. Apple and Microsoft alone account for roughly 7% of the entire index — so when these giants move, the whole index feels it.
How is the S&P 500 Different from the Stock Market?
This is a common source of confusion. People say “the market is up” when they mean “the S&P 500 is up” — but they’re not exactly the same thing.
The U.S. stock market contains over 5,000 publicly traded companies. The S&P 500 only includes 500 of them — but these 500 companies represent approximately 80% of the total value of the entire U.S. stock market.
So while the S&P 500 isn’t literally the whole market, it’s close enough that most investors treat it as a reliable proxy. When people say “the market,” they almost always mean the S&P 500.
Why Does Everyone Talk About the S&P 500?
Because over the long term, it has delivered remarkable results.
Here’s what the S&P 500 has done historically:
| Time Period | Average Annual Return |
|---|---|
| Since 1957 (inception) | ~10.5% per year |
| Last 30 years | ~10.7% per year |
| Last 10 years | ~13.1% per year |
To put that in perspective:
If you had invested $10,000 in an S&P 500 index fund in 1994 and never touched it, by 2024 it would have grown to approximately $200,000 — purely through market growth and reinvested dividends.
That’s not a typo. $10,000 → $200,000 in 30 years, without picking a single stock.
This is why Warren Buffett — widely considered the greatest investor of all time — has repeatedly said that for most people, a low-cost S&P 500 index fund is the best investment they can make.
What Happens When the S&P 500 Drops?
Drops happen — and they’re a normal part of investing. Here’s some historical context:
| Event | S&P 500 Drop | Recovery Time |
|---|---|---|
| 2000–2002 Dot-com Crash | -49% | ~7 years |
| 2008–2009 Financial Crisis | -57% | ~5.5 years |
| 2020 COVID Crash | -34% | ~5 months |
| 2022 Rate Hike Selloff | -25% | ~1 year |
Notice something? The S&P 500 has recovered from every single crash in its history.
The investors who lost money permanently were those who panic-sold during the drops. The investors who stayed patient — or even bought more during the dips — came out ahead every time.
This is the core argument for long-term index investing: you don’t need to predict the market. You just need to not panic.
How Do You Actually Invest in the S&P 500?
You can’t directly buy “the S&P 500” — it’s just an index, a list. But you can buy ETFs and index funds that track it.
The most popular S&P 500 ETFs are:
VOO — Vanguard S&P 500 ETF
- Expense ratio: 0.03%
- One of the most popular ETFs in the world
- Ideal for long-term investors
SPY — SPDR S&P 500 ETF Trust
- Expense ratio: 0.0945%
- The oldest ETF in the U.S. (launched 1993)
- Most heavily traded ETF in the world
IVV — iShares Core S&P 500 ETF
- Expense ratio: 0.03%
- BlackRock’s version; nearly identical to VOO
All three track the same index — the S&P 500. The main differences are the expense ratio (annual fee) and the company that manages them. For long-term buy-and-hold investors, VOO and IVV are typically preferred due to their rock-bottom fees.
We’ll do a full deep-dive comparison of VOO vs SPY vs IVV in a future post.
S&P 500 vs. Other Indexes
The S&P 500 isn’t the only index out there. Here’s how it compares to other popular ones:
| Index | Companies | Focus |
|---|---|---|
| S&P 500 | 500 | Large U.S. companies |
| Dow Jones (DJIA) | 30 | 30 selected blue-chip companies |
| NASDAQ-100 | 100 | Top 100 NASDAQ companies (mostly tech) |
| Russell 2000 | 2,000 | Small U.S. companies |
| Total Stock Market | ~3,500+ | Nearly all U.S. public companies |
The S&P 500 sits in the sweet spot — broad enough to be representative, focused enough on established companies to be relatively stable.
Is the S&P 500 Right for Every Investor?
For most long-term investors, yes — it’s an excellent foundation. But it’s worth knowing a few limitations:
It’s U.S.-only. The S&P 500 only covers American companies. International diversification requires additional investments.
It’s large-cap heavy. Small and mid-sized companies are not well represented. Some investors prefer broader total market funds like VTI for this reason.
It’s tech-heavy. The top 10 holdings are heavily concentrated in technology. A major tech downturn would hit the index hard.
It doesn’t guarantee short-term gains. Over any given 1–3 year period, the S&P 500 can and does lose money. It’s a long-term vehicle.
Despite these limitations, for most everyday investors building long-term wealth, the S&P 500 remains one of the most reliable tools available.
Key Terms to Remember
| Term | Simple Definition |
|---|---|
| S&P 500 | An index tracking 500 of the largest U.S. companies |
| Index | A list of stocks used to measure market performance |
| Market cap | Total value of a company’s shares (price × shares outstanding) |
| Market-cap weighted | Larger companies have more influence on the index |
| Benchmark | A standard used to measure investment performance |
| VOO / SPY / IVV | Popular ETFs that track the S&P 500 |
Final Thoughts
The S&P 500 isn’t just a number on a screen. It’s a reflection of the U.S. economy, a benchmark for professional investors, and for many everyday people — the foundation of their entire investment strategy.
Understanding what it is and how it works is one of the most important things you can learn as a new investor.
In the next post, we’ll go one level deeper and look at the most popular S&P 500 ETF in the world: VOO. What is it exactly, how does it work, and is it the right choice for you?
See you there.
— BaselineJay
Disclaimer: This post is for informational and educational purposes only and should not be considered financial advice. Always do your own research before making any investment decisions. Past performance does not guarantee future results.
Previously: What is an ETF? How It Works and Why It Matters ←