Watch how the S&P 500 is actually calculated.

Unlike previous indexes from S&P, the S&P 500 could be computed in real time using computer technology that tracked stock tickers across stock exchanges. This innovation is partly what led to 500 companies being listed on the index, a huge increase from the 90 companies in S&P's flagship index when the company had to do all the analysis by hand.

Stocks are added to the S&P 500 by a secret selection committee that meets regularly to assess which companies can remain in the index, which companies need to be added, and which companies no longer meet the criteria. The members of the committee used to be public, but S&P Global decided to keep its members confidential after companies sent packages, letters, and gifts to try to make it into the index.

Also run by S&P Dow Jones Indices, the S&P 500 tracks 500 large US firms using market-value weighting. Many analysts view it as a more accurate gauge of the American economy.

When the S&P 500 index was released in 1957, it was helpful for investors, but not necessarily profitable. S&P Global now makes more than $1B a year just from selling its index data. Alongside its other services, like credit ratings, S&P Global makes more than $14B a year.

While the decision to add a company to the index is ultimately up to the selection committee, any prospective company has to meet some criteria to be considered. To join, the company must have been profitable for the last four quarters, must have a market capitalization exceeding $22.7B, and meet certain requirements around tradeable stock availability (or float).

Since the index represents a broad range of diverse industries, it's become a proxy for the market itself and a common benchmark for investors to compare returns and performance patterns against. Generally speaking, when someone says a stock is under- or out-performing the market, that actually means under- or out-performing the S&P 500. The S&P 500 is exchange-agnostic, and includes companies listed on both the NYSE and Nasdaq.

Since some large companies have dual-class stock structures (like Alphabet and Fox Corporation), there are multiple listings on the S&P 500 for the same company. S&P Global has banned and then reversed bans on companies with dual-class structures multiple times since first allowing dual-class stocks in 2014.

The S&P 500 is primarily composed of large-cap companies. The idea is that the index provides a big-picture view of the economy by assessing the performance of many of the largest public companies across different industries. The median market capitalization of companies listed on the S&P 500 is around $40B.

Some critics of the S&P 500's selection process argue that human involvement makes it an actively managed index. S&P Global maintains that while a human selects the stocks in the index, those decisions are not made with the intent of maximizing performance, but rather, to provide a snapshot of the largest companies across different industries.

From the 1941 merger of Standard Statistics and Poor's Publishing to the creation of the S&P 500 in 1957, the company that created the famous index has long been a leader in financial intelligence.

The Dow and S&P 500 are both indexes meant to provide a broad representation of the economy. The Dow has 30 companies and is weighted by share price, while the S&P 500 has 500 different companies weighted by market capitalization. Since the indexes are so different, investors don't always agree on which index is a better representation of the economy—though the two move in the same direction more than 90% of the time.

State Street, a popular ETF issuer, is responsible for the SPDR S&P 500 ETF. This fund trades under the SPY ticker, and State Street maintains a web page with key facts and figures on SPY. For instance, its expense ratio is 0.0945%, or $9.45 on an initial $10K investment.

The S&P 500 is a market-cap-weighted index, which means companies with larger market capitalizations have a larger impact on the index's overall performance. Many of the top companies in the index are currently tech companies—including Nvidia, Microsoft, Alphabet, and Apple—that all have large investments in artificial intelligence. As a result, some analysts are concerned that the index is overly exposed to risky AI investments.

In a given year, the value of the S&P 500 can significantly fluctuate. An intra-year drawdown is the most significant difference between the index's peak and lowest point.

This raised concerns for investors about the index's risk exposure. As many large tech companies continued posting record highs, analysts argued that the top-heavy index was becoming less representative of the economy as a whole.

Unlike many indices, the Dow has no strict rules for inclusion. A small committee at S&P Dow Jones Indices uses judgment—favoring companies with strong reputations, steady growth, and broad investor interest.

To adjust for stock splits, mergers, and replacements, the DJIA uses a figure called the Dow Divisor. Originally valued around 12 in 1896, and now less than one, it ensures today’s index levels remain comparable with the past.

Since the S&P 500 is considered a bellwether index (meaning it represents the health of the US economy), its value is important for investors in both bull and bear markets. The S&P 500 has been impacted by recessions and downturns, from the 1970s oil crisis to the dot-com crash of the early 2000s.

Stock markets and the indexes that track their biggest companies tend to ebb and flow, with long growth periods punctuated by shorter recessions. Track the 60-year history of one of the most common stock market indexes, the S&P 500, with this data visualization. The chart highlights the long-term durability of markets despite appearance of short-term volatility.

Unlike most indices, which weigh companies by market value, the DJIA is price-weighted—meaning higher-priced stocks have more influence on its movements. As a result, a company’s share price matters more than its overall size.

John Bogle, the founder of The Vanguard Group, created a fund that tracked the S&P 500 in 1976. That fund created an unprecedented opportunity for individual retail investors, brought down fees across the board, and popularized the belief that passive, low-cost index fund investments would outperform actively managed portfolios long-term.

David Blitzer, the former index chair at S&P Global, earned the nickname "gatekeeper" of the stock market after helping decide which companies made it into the S&P 500 for 24 years. Blitzer became a legend in the world of indexing and has a reputation for being even-tempered and always wearing a bow tie.

With only 30 companies and a price-weighted formula, skeptics say the DJIA underrepresents vast sectors of the market. They claim it is outdated, though its close correlation with the broader S&P 500 keeps it relevant.

That's partly because there isn't readily available stock information, and financial accounting is kept behind closed doors. Typically, determining the value of a private company involves, among other things, closely comparing the private company with its competitors.

Dividend aristocrats are considered the best of the best on the S&P 500—all with market capitalizations above $3B, more than $5M in daily trading volume, and consecutive dividend growth for a minimum of 25 years. Some examples of dividend aristocrats are Coca-Cola, Procter & Gamble, and Walmart.

The Dow Jones Industrial Average tracks 30 large U.S. companies from all major U.S. sectors except for utilities and transportation. It's considered a bellwether of the U.S. economy.

Liquidity. Forex. Capitalization. Blue chip stocks. These are just a few pieces of stock market vocabulary most people who don't spend all day on a trading floor might not know. Thankfully, we found a fun infographic that makes it easier to learn what 40 key stock market terms mean and why each of them matters.

This 3,000+ company index stands in contrast to the Nasdaq 100, which only includes 100 of the most influential non-financial companies traded on the exchange. These are the two most commonly used indices for Nasdaq investments.

Instead of purchasing individual stocks and bonds, new investors may want to start in funds that track an index—like the S&P 500—or that hold a group of themed stocks.

Open any newspaper, turn on your local TV news station, or listen to a daily business radio segment, and you’re bound to hear about how the stock market is performing. Netflix created a 17-minute (free) explainer that dives deep into the nitty-gritty of how we got here.

Charles Dow introduced the DJIA on May 26, 1896, as a simple average of 12 industrial stocks. Although it became the nation’s most enduring market index, none of its original companies remain in the Dow today.

Since 1928, the DJIA has included 30 firms. Today's group spans technology, healthcare, and finance—with Apple, Microsoft, JPMorgan Chase, Pfizer, and Coca-Cola among its most recognized components.

In 1996, more than 7,300 companies traded publicly on US stock markets, but that number has recently dropped to 4,300. Economists point to two reasons: First, going public requires full disclosure of operations, exposing it to scrutiny from investors, competitors, and analysts. Second, the IPO process is expensive and time-consuming.

While public companies typically have the highest valuations, private companies get close. This list breaks down the top 50 as of 2025, with SpaceX at the top with a value of $350B, followed by ByteDance. Over three-fifths of the list are located in the US, with eight in China.

These seven companies are Alphabet, Amazon, Apple, Meta, Microsoft, Nvidia, and Tesla. They're often responsible for over 40% of the Nasdaq 100 index's gains, but the exact percentage varies from year to year.

To file for an IPO, a company must file a registration form called an S-1 or prospectus with the US Securities and Exchange Commission. S-1s detail a company's current business model, competitive landscape, and other financial information.

This index was created in 1985, over a decade after the Nasdaq first launched. The companies on the index must meet certain criteria, including having a minimum average daily trading value of $5M.