The S&P 500 and How It Works

How the S&P 500 Tells You About America's Health

what to know about the s&P 500

The Balance / Hilary Allison

The S&P 500 is a stock market index that tracks the stocks of 500 large-cap U.S. companies. It represents the stock market's performance by reporting the risks and returns of the biggest companies. Investors use it as the benchmark of the overall market, to which all other investments are compared.

S&P stands for Standard and Poor, the names of the two founding financial companies. It was officially introduced on March 4, 1957 by Standard & Poor. McGraw-Hill acquired it in 1966. The S&P Dow Jones Indices owns it as of 2022 and that's a joint venture between S&P Global (formerly) McGraw Hill Financial, CME Group, and News Corp, the owner of Dow Jones.

The S&P 500 had an average 10-year annual return of 13.9% as of Jan. 7, 2022.

Key Takeaways

  • Investors usually look at the S&P 500 to assess how the overall stock market is doing. This index is considered a leading U.S. economic indicator.
  • It tracks 500 publicly traded, large-cap U.S. companies. These businesses must meet specific criteria to be a part of the S&P 500. The mix of industries that make up the S&P 500 list often reflects the economic makeup of the United States.
  • Investors can purchase shares of stocks listed on the S&P 500 or invest in index funds that track the S&P 500.

How the S&P 500 Works

The S&P 500 tracks the market capitalization of the companies in its index. Market cap is the total value of all shares of stock that a company has issued. It's calculated by multiplying the number of shares issued by the stock price. A company that has a market cap of $100 billion receives 10 times the representation as a company whose market cap is $10 billion. The total market cap of the S&P 500 was $34 trillion as of January 2022. 


The index is weighted by a float-adjusted market cap. It only measures the shares available to the public. It does not count those held by control groups, other companies, or by government agencies.

A committee selects each of the index's 500 corporations based on their liquidity, size, and industry. It rebalances the index quarterly, in March, June, September, and December.

A company must be in the United States and have an unadjusted market cap of at least $13.1 billion to qualify for the index. At least 50% of the corporation's stock must be available to the public. Its stock price must be at least $1 per share. It must file a 10-K annual report. At least 50% of its fixed assets and revenues must be in the United States. Finally, it must have at least four consecutive quarters of positive earnings.

The stock can't be listed on pink sheets or traded over the counter. It must be listed on the New York Stock Exchange, Investors Exchange, Nasdaq, or BATS Global Markets.

As of January 7, 2022, the ten largest companies, with a weighted market cap, in the S&P 500 were:

  1. Apple Inc. (AAPL)
  2. Microsoft Corp. (MSFT)
  3. Inc. (AMZN)
  4. Alphabet Inc. A (GOOGL)
  5. Tesla, Inc (TSLA)
  6. Alphabet Inc. C (GOOG)
  7. Meta Platforms, Inc. Class A (FB)
  8. Nvidia Corp. (NVDA)
  9. Berkshire Hathaway B (BRK.B)
  10. Unitedhealth Group Inc. (UNH)


The makeup of the S&P 500 industries reflects that of the economy.

As of January 7, 2022, the S&P 500 sector breakdown included:

  • Information Technology: 29.2%
  • Health Care: 13.3%
  • Consumer Discretionary: 12.5%
  • Financials: 10.7%
  • Communication Services: 10.2%
  • Industrials: 7.8%
  • Consumer Staples: 5.9%
  • Real Estate: 2.8%
  • Energy: 2.7%
  • Materials: 2.6%
  • Utilities: 2.5%

S&P 500 vs. Other Stock Market Indexes

The S&P 500 has more large-cap stocks than the Dow Jones Industrial Average. The Dow tracks the share price of 30 companies that best represent their industries. Its market capitalization accounts for almost one quarter of the U.S. stock market. The Dow is the most quoted market indicator in the world.

The S&P 500 has fewer technology-related stocks than the Nasdaq. As of June 2021, 55% of Nasdaq allocations were in information technology compared to 28% for the S&P 500.

All these stock indexes tend to move together despite their differences. You can still understand how well the stock market is generally doing if you focus on only one. You don't have to follow all three.

Milestones of the S&P 500

The following table shows various milestone events of the S&P 500, including both highs and lows, and other memorable moments.

June 4, 1968 100.38 First time above 100
Oct. 19, 1987 224.84 Black Monday
March 24, 1995 500.97 First close above 500
Feb. 2, 1998 1,001.27 First close above 1,000
Oct. 9, 2007 1,565.15 Highest close before financial crisis
Oct. 13, 2008 1,003.35 Largest % gain of 11.6%
Aug. 26, 2014 2,000.02 First close above 2,000
Sept. 21, 2018 2,929.67 New record high
July 12, 2019 3,013.77 First close above 3,000
March 12, 2020 2,480.64 Largest % decline since Black Monday, entered bear market
March 23, 2020 2,237.40 Stock crash low
August 18, 2020 3,389.78 New record high end of bear market
August 28, 2020 3,508.01 Closes above 3,500
April 1, 2021 4,019.87 Closes above 4,000
Oct. 13, 2021 4,519.63 Closes above 4,500

How to Use the S&P 500 to Make Money

You can't invest in the S&P, but you can mimic its performance with an index fund. You could also buy shares of stocks that are in the S&P 500.


You can weigh the stocks in your portfolio according to their market cap, as the S&P does.

You can use the S&P 500 as a leading economic indicator of how well the U.S. economy is doing. Investors tend to buy stocks when they're confident in the economy.

Since the S&P 500 only measures U.S. stocks, monitoring foreign markets may help provide a global view, such as emerging markets like China and India. You could also consider holding a small percentage of your investments in commodities, such as gold, which might hold their value longer when stock prices decline.

Besides following the S&P 500, following the bond market might help with your investment goals. Standard & Poor's also gives bonds credit ratings. Although bond prices tend to move in the opposite direction of stock prices, that's not always the case. Both bond and stock prices can be volatile at times.

There are many different types of bonds. They include Treasury bonds, corporate bonds, and municipal bonds. Bonds provide some of the liquidity that keeps the U.S. economy lubricated. Bonds can also impact mortgage interest rates.

Frequently Asked Questions (FAQs)

How do you invest in the S&P 500?

You can't invest directly in the S&P 500, but you can invest in specific companies that are included in its index. You can also invest in S&P 500 index funds that are designed to closely follow the performance of the S&P 500.

What companies are in the S&P 500?

Companies must have an unadjusted market cap of at least $13.1 billion in order to qualify for inclusion in the S&P 500. They must also meet specific criteria in terms of liquidity and profitability.

What does the S&P 500 measure?

The S&P 500 tracks the value of the 500 stocks in its index at any given time. These stocks represent 500 of the largest companies in the U.S. based on market capitalization.

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The Balance uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. S&P Global. “Our History. Who We Are.”

  2. S&P Dow Jones Indices. "S&P 500."

  3. S&P Dow Jones Indices. "Data - Quick Facts."

  4. S&P Dow Jones Indices. "S&P U.S. Indices Methodology," Pages 6-9, 36.

  5. S&P Dow Jones Indices. "At a Glance: The Dow vs. the S&P 500."

  6. Nasdaq. "When Performance Matters: Nasdaq-100 vs. S&P 500 First Quarter 21."

  7. Yahoo! Finance. "S&P 500 (^GSPC)."

  8. Institutional Investor. "Stocks and Bonds Have Moved in Opposite Directions for Decades. Here’s What Could Change That."

  9. U.S. Securities and Exchange Commission. "Interest Rate Risk — When Interest Rates Go Up, Prices of Fixed-Rate Bonds Fall."

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