Information Technology was 39.27% of the S&P 500 on 12 October 2026. The S&P 500 is the index of 500 large US companies. Materials, the sector holding chemicals and mining, was 1.62% on the same day.
Both numbers come from the same filing system. It sorts listed companies worldwide into one of 11 groups, so it decides what a "technology fund" actually owns. This guide explains the 11 sectors, who sets them, where the lines fall and how to use them.
What are the 11 stock market sectors? They are the top level of the Global Industry Classification Standard (GICS). Two index companies (S&P Dow Jones Indices and MSCI) use it to sort every listed company by what it mainly does, so each company sits in exactly one sector.
The 11 are Energy, Materials, Industrials, Consumer Discretionary, Consumer Staples, Health Care, Financials, Information Technology, Communication Services, Utilities and Real Estate.
The sectors are very unequal. Weighted by company size, Information Technology was 39.27% of the S&P 500 on 12 October 2026, while Materials was 1.62%.
A company goes where most of its revenue comes from, which is why Amazon and Tesla both sit in Consumer Discretionary instead of Information Technology.
What GICS is and who runs it
GICS stands for the Global Industry Classification Standard. S&P Dow Jones Indices and MSCI created it in 1999 and still own it jointly. It is the classification behind the S&P 500's sector indices and behind most sector funds.
GICS has four levels. There are 11 sectors at the top, then 25 industry groups, then 74 industries, then 163 sub-industries at the bottom. A pharmaceutical company and a hospital chain share the Health Care sector, but they sit in different sub-industries.
A company is placed by its principal business activity, meaning the activity that produces most of its revenue. Where a company has several business lines, earnings and how the market values it are considered too. Classifications are reviewed every year.
The 11 sectors and what sits in each
Energy: oil and gas producers, refiners, drillers, pipelines.
Materials: chemicals, metals, mining, packaging, construction materials.
Industrials: aerospace, defence, machinery, railways, airlines, staffing.
Consumer Discretionary: cars, hotels, restaurants, clothing, online retail.
Consumer Staples: food, drinks, tobacco, household goods, supermarkets.
Health Care: drugmakers, biotechnology, medical devices, health insurers.
Financials: banks, insurers, asset managers, exchanges, card networks.
Information Technology: software, semiconductors, hardware, technology services.
Communication Services: telecoms, media, search, social networks, video games.
Utilities: electricity, gas and water suppliers.
Real Estate: real estate investment trusts and property managers.
The split is often about who pays and when. A supermarket sells food, bought in every economy, so it is a staple. A hotel stay is discretionary spending, so it sits in Consumer Discretionary.
The sector weights in the S&P 500
Source: State Street; YX Insights
The three smallest sectors together, Utilities, Real Estate and Materials, came to 5.26% of the S&P 500 on 12 October 2026. Information Technology was 7.5 times that combined figure.
This matters for anyone holding an index fund. A fund tracking the S&P 500 is weighted by company size, so almost 2/5 of it sat in one sector on that date. The sector weights move with prices, so they are worth rechecking.
Sectors move very differently
The sector funds below hold only the S&P 500 companies in one sector. SPY (the S&P 500 exchange-traded fund, or ETF) covers all 11 at once, while the Information Technology fund (XLK) covers one.
Source: YX Insights price data
Each line starts at 100 at the end of 2018, so a line at 678 means a gain of 578%. From the end of 2018 to 13 October 2026, with dividends counted, the Information Technology fund returned 578.0%. The Health Care fund (XLV) returned 123.8%.
The S&P 500 itself returned 249.1%, with Communication Services (XLC) at 193.3% and Financials (XLF) at 166.0%. The gap between Information Technology and Health Care was 454.1 percentage points since the end of 2018.
Choosing a sector mattered more to the result than choosing the index did.
When the sector list changed
The 11 sectors have not always been 11. Companies have moved between them as well. Three changes make old sector data differ from new.
Real Estate was carved out of Financials after the close on 31 August 2016, taking the count from 10 to 11. It was the first sector added since GICS began.
Telecommunication Services was broadened and renamed Communication Services after the close on 28 September 2018. Companies moved in from Information Technology and from the media part of Consumer Discretionary. Meta Platforms, Alphabet, Netflix and Walt Disney all sit there today.
Then, after the close on 17 March 2023, payment companies left Information Technology for Financials. Visa and Mastercard became Financials holdings. The two of them were 14.77% of the Financials sector index on 12 October 2026. Neither company lends.
Target moved the other way in that same change, from Consumer Discretionary to Consumer Staples. A longer story on the payment networks sits in how a card payment works.
More is coming. S&P Dow Jones Indices and MSCI opened a consultation on 17 July 2026 on restructuring the Semiconductors sub-industry and on how to classify artificial intelligence businesses. It closes on 30 October 2026, with any changes to be announced by November 2026.
Why Amazon and Tesla sit in Consumer Discretionary
Amazon sells goods to shoppers, so its largest revenue line puts it in Consumer Discretionary, next to clothing shops. Tesla sells cars, which are a discretionary purchase. Neither is classed as a technology company.
How much of a sector index sits in its two largest companies
Source: State Street; YX Insights
Amazon and Tesla together were 41.95% of the Consumer Discretionary sector index on 12 October 2026. Communication Services was more concentrated still, at 46.52% in Meta Platforms and Alphabet, counting Alphabet's two share classes as one company.
The other three sectors on the chart are less concentrated, though not by much. Information Technology held 29.13% in Nvidia and Apple. Health Care held 25.37% in Eli Lilly and Johnson & Johnson. Financials held 23.91% in Berkshire Hathaway and JPMorgan Chase.
Buying a sector fund is often closer to buying two companies than to spreading money across an industry.
How to use sectors in practice
Check what a sector fund actually holds before treating it as a bet on a theme. The label names the sector, while the weights name the companies.
Use sectors to compare like with like. A price-to-earnings ratio means something different in Utilities than in Information Technology, so the sector is the fair comparison group.
Remember that a sector is not a supply chain. Nearly every company in the chip chain sits in Information Technology, from the designers to the machine makers, as the semiconductor value chain sets out.
Sectors are a filing system. Knowing which of the 11 a company sits in tells you who it is measured against, what moves its shares alongside it and what you already own.
Common questions about stock market sectors
How many stock market sectors are there?
There are 11. They are Energy, Materials, Industrials, Consumer Discretionary, Consumer Staples, Health Care, Financials, Information Technology, Communication Services, Utilities and Real Estate. Below them GICS has 25 industry groups, 74 industries and 163 sub-industries, so a sector can be broken down much further.
What sector is Amazon in?
Consumer Discretionary. GICS places a company by the activity that produces most of its revenue. Most of Amazon's comes from selling goods to shoppers. Tesla sits in the same sector, because cars are a discretionary purchase. Together they were 41.95% of the Consumer Discretionary sector index on 12 October 2026.
Who decides which sector a company is in?
S&P Dow Jones Indices and MSCI, the two index companies that own GICS. They created it in 1999, review company classifications every year and change the structure itself from time to time. The latest consultation on the structure opened on 17 July 2026 and closes on 30 October 2026.
What is the biggest sector in the S&P 500?
Information Technology, at 39.27% of the index on 12 October 2026. Financials was second at 11.52%. The smallest was Materials at 1.62%. The weights follow company size, so they shift with prices, which makes it worth checking the current figure.
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