What is the S&P 500?
The S&P 500 is a scoreboard for the 500 biggest public companies in America — Apple, Nvidia, JPMorgan, ExxonMobil and 496 others. When someone says “the market was up today”, this is almost always the number they mean.
500
Large-cap U.S. companies
rebalanced quarterly
~$44T
Combined market cap
roughly 80% of U.S. equities
1957
Index launched
modern form, S&P Dow Jones Indices
01Read it
America's corporate leaderboard
Think of the index as a corporate leaderboard. A committee at S&P decides who is on it, and companies have to keep meeting the standards on the right to stay there.
It is also not the tech index people assume it is. Healthcare, banking, retail, energy and manufacturing all sit in there alongside the software and chip companies that dominate the headlines.
Entry requirements
- U.S. listedTrades on NYSE or Nasdaq
- Market cap $22.7B+As of early 2026
- 4 profitable quartersPositive GAAP earnings
- High liquidityActive trading volume
~3 companies replaced per quarter on average
Why does the S&P 500 matter?
There are thousands of public companies in the United States, and nobody tracks them one by one. The S&P 500 compresses the important ones into a single number, which is why it is the figure the evening news reads out.
When it rises, most of America's largest companies are worth more than they were yesterday. When it falls, they are worth less. That is the entire signal — it says nothing about small companies, about bonds, or about the economy you actually live in.
Why do bigger companies matter more?
Not every company in the S&P 500 counts equally. The index is market-cap weighted: the bigger a company is, the more of the index it makes up, and the more its share price moves the whole number.
Apple alone is 6.34% of the index. Put $100 into an S&P 500 index fund and about $6.34 of it goes to Apple — while each of the smaller companies near the bottom of the list gets a few cents.
Can you invest in the S&P 500?
Not directly — the index is a list, and a list has no shares to buy. What you can buy is a fund that tracks it: an index fund or an ETF that holds the same 500 companies at the same weights.
That is the whole appeal. One purchase, a few dollars in fees a year, and you own a sliver of every company on the leaderboard.
02See it
29 green years. 7 red ones.
The red bars look scary — but they're rarer, and every one of them was followed by a recovery.
Year to year the S&P 500 is unpredictable. Stretched over decades, the pattern is lopsided: since 1990, 29 of 36 years ended up and only 7 ended down — about four green years for every red one.
The red years are the ones people remember. 2008 took 37% off the index in twelve months. If you had bought at the start of that year and simply held, you were back to even by 2012 and had doubled your money by 2017.
But recovery is not a schedule. Buy at the start of 2000 instead and you finish six years in a row below where you started; twelve years in, you are up less than 7%. The long-run average hides how different two starting points can be.
Total return, dividends reinvested. Illustrative. Not investment advice.
Who's actually inside
Ten companies out of 500 carry 37% of the index, and 22 of those 37 points are technology. A 500-company fund is less spread out than it sounds — when the big tech names move sharply, the whole index moves with them.
- #1
NVDANVIDIA7.37% - #2
AAPLApple6.34% - #3
MSFTMicrosoft4.30% - #4
AMZNAmazon3.80% - #5
GOOGLAlphabet A3.36% - #6GOOGAlphabet C3.13%
- #7
AVGOBroadcom2.69% - #8
TSLATesla2.26% - #9
METAMeta2.13% - #10
MUMicron1.64%
Approximate weights, June 2026. For illustrative purposes only. Not investment advice.
03Try it
The time machine
Pick a year, drop in some money, and see what the real S&P 500 returns would have done to it. Try starting in 2000 or 2008 — right before the crashes.
What if you'd invested?
Worth end of 2025
$7,528
Total return
+653%
Years invested
26
Compounds real annual total returns, 1990–2025. Before fees and inflation. Illustrative only — not investment advice.
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