S&P 500

In 1860 Henry Varnum Poor published “History of the Railroads and Canals of the United States” to give investors data on the U.S. railroad industry. In 1906 Luther Lee Blake founded the Standard Statistics Bureau to provide current information on non-railroad industrials. In 1941 Standard Statistics merged with Poor’s Publishing to form Standard and Poor’s.⁠[1]

In 1923 the Standard Statistics Company began calculating the S&P Composite Index, a weekly, cap-weighted index of 233 companies in 26 industries. The S&P 90 of 1926 was a cap-weighted index of 90 companies updated daily.⁠[2]

On February 27, 1957, Standard & Poor’s introduced the Standard “500” at a press luncheon. Its 500 stocks, 425 industrials, 25 rails and 50 utilities, accounted for over 90% of total U.S. market value, and an electronic method developed by Melpar, Inc. allowed the index to be calculated and distributed hourly.⁠[3]

The S&P 500’s launch date is March 4, 1957, and its base period is 1941–1943 with a base value of 10.⁠[4]

On April 21, 1982, the Chicago Mercantile Exchange began trading futures based on the S&P 500, and on July 1, 1983, options on the index began trading on the Chicago Board Options Exchange. On October 19, 1987, the index fell 20.47%, its worst daily percentage loss.⁠[5]

In 1986 the index’s intraday calculation frequency rose from once a minute to once every 15 seconds.⁠[2]

In January 1993 the SPDR S&P 500 ETF (SPY) debuted as the first U.S.-listed ETF, with roughly $6.5 million in assets.⁠[6]

In 1999 S&P and MSCI developed the Global Industry Classification Standard (GICS) to establish a global standard for classifying companies. The S&P 500 Sector Indices, weighted by float-adjusted market capitalization, are direct slices of the S&P 500 based on GICS.⁠[7]

On December 8, 2004, Standard & Poor’s announced a float adjustment schedule for the S&P 500 and affiliated indices. On March 18, 2005, the indices moved to half float adjustment, so a company with an 80% float factor would count at 90%. On September 16, 2005, all official U.S. indices moved to full float adjustment.⁠[8]

On July 2, 2012, McGraw-Hill and CME GroupCME GroupCME Group is a Chicago-based derivatives exchange group that owns four exchanges, CME, CBOT, NYMEX and COMEX, and the CME Clearing clearing house, and also runs cash trading platforms including BrokerTec and EBS. Its origins go back to the Chicago Butter and Egg Board, formed in 1898; it became the first publicly traded exchange in the United States in 2002 and took its current name after merging with the Chicago Board of Trade in 2007.Open the full entry announced the launch of S&P Dow Jones Indices. McGraw-Hill owned 73%, CME Group 24.4% through affiliates and Dow Jones & Company 2.6% indirectly, and Alexander Matturri was named chief executive. CME Group received a long-term exclusive license to use the S&P 500 for futures and options on futures.⁠[9]

The S&P Dow Jones Indices LLC joint venture, established in June 2012, is now owned 73% by S&P Global and 27% by CME Group.⁠[10]

In April 2014 GoogleGoogleGoogle is an American technology company founded by Larry Page and Sergey Brin and incorporated in 1998. It became an Alphabet subsidiary in 2015. Its businesses include internet search, advertising, software platforms, cloud computing, and artificial intelligence.Open the full entry’s new non-voting Class C shares kept the ticker GOOG while its Class A shares took the ticker GOOGL, and both classes entered the index, giving it 500 companies but 501 stocks. Under the plan then announced, from September 15, 2015, constituents with multiple share classes would have all their liquid classes included.⁠[11]

On July 31, 2017, S&P Dow Jones Indices said the S&P Composite 1500 and its component indices, including the S&P 500, would no longer add companies with multiple share class structures. Existing constituents were grandfathered.⁠[12]

The move followed FTSE Russell in excluding companies such as Snap Inc. whose shares carry limited or no voting rights.⁠[13]

On April 17, 2023, S&P Dow Jones Indices announced consultation results making all companies with multiple share class structures eligible for addition to the S&P Composite 1500 and its component indices, effective immediately, if they met all other criteria. Tracking stocks remained ineligible.⁠[14]

On July 1, 2025, S&P Dow Jones Indices raised the company market capitalization guideline for the S&P 500 from US$20.5 billion to US$22.7 billion, effective the same day.⁠[15]

As of December 31, 2025, assets indexed to the S&P 500 totaled about US$15.74 trillion, including about US$3.01 trillion in ETPs, US$7.74 trillion in non-ETP products and US$4.99 trillion in exchange-traded derivatives. Benchmarked assets were about US$7.61 trillion, for a total of about US$23.35 trillion.⁠[16]

At the end of 2025 the index’s 500 companies accounted for approximately 90% of total U.S. equity market capitalization. The index “does not necessarily include the largest 500 U.S.-domiciled companies”: candidates must meet criteria such as positive earnings, liquidity and size thresholds, and the Index Committee also considers sector balance.⁠[17]

On January 28, 2026, the S&P 500 rose about 0.3% in early trading to a record 7,002.28, its first move past 7,000, before slipping back below that level.⁠[18][19]

On April 15, 2026, the index rose 0.8% to close at a record 7,022.93.⁠[20]

On March 18, 2026, S&P Dow Jones Indices announced that it had licensed the S&P 500 to Trade[XYZ] for a perpetual contract on the Hyperliquid blockchain, tradable 24/7 and open to eligible investors including non-U.S. investors. S&P DJI described it as the first officially licensed S&P 500 perpetual.⁠[31]

On May 27, 2026, S&P Dow Jones Indices announced that the Texas Stock Exchange (TXSE) would become an eligible exchange for the S&P U.S. Indices, including the S&P 500, effective when continuous trading on TXSE begins, targeted for July 6, 2026.⁠[32]

On June 4, 2026, S&P DJI published the results of its consultation on megacap companies. The Index Committee made no changes to eligibility criteria for the S&P 500, S&P MidCap 400 or S&P SmallCap 600, and did not adopt proposals such as shortening IPO seasoning from 12 to six months or waiving the minimum IWF.⁠[33]

As of September 2026, the S&P 500 comprised 503 stocks issued by 500 companies, because a few constituents have more than one class of stock in the index, such as Alphabet’s Class A and Class C shares.⁠[34]

As of September 30, 2026, the S&P 500 stood at 7,652, up 12.75% year to date and down 0.35% over one month.⁠[35]

The S&P 500 is a float-adjusted market-cap-weighted index: each stock’s weight reflects its price times shares outstanding adjusted for public float, which excludes large blocks held by founders, executives or government agencies. The index level is the sum of constituent market values divided by a divisor, published in price return and total return versions. Constituent changes may be made at any time.⁠[36]

Under the July 2026 methodology, candidates must be U.S.-domiciled, with a float-adjusted liquidity ratio of at least 0.75, an IWF of at least 0.1, and positive GAAP earnings for the latest quarter and the trailing four quarters. An Index Committee meets monthly and makes changes as needed.⁠[4]