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Know your sectors and industries

One way to invest with the business cycle and diversify an equity portfolio is using sector-based securities and funds. In order to employ this type of strategy, you should know how sectors and industries are comprised.

Different approaches

Thinking of the market in terms of sectors can be advantageous for investors; however, sorting stocks into separate sectors and industries may not be as clear cut as it may seem. This may be due in part to companies belonging to different industries, depending on the criteria used. Most classification systems use one of two approaches to sort companies into industries and sectors; the production-oriented approach and the market-oriented approach.

The production-oriented approach focuses on grouping companies that produce similar products or use similar inputs used in the manufacturing process. In production-oriented approaches, many companies that manufacture products are classified differently than those that provide services, for example.

The market-oriented approach focuses on classifying companies by the markets they serve, rather than on the products they produce. In addition to how the company earns revenue, this approach also focuses on how customers use the company’s products.

Sector classification structures

There are 3 main classification schemas: The Global Industry Classification Standard (GICS), the Industry Classification Benchmark (ICB), and the Thomson Reuters Business Classification (TRBC).

These classification schemas are designed for creating benchmarks and to provide an acceptable and meaningful method for standardizing industry definitions so that comparison and analysis can be conducted between companies, industries, and sectors worldwide.

Comparison of major sector classification systems

Level/System GICS ICB TRBC
1st 11 Sectors 11 Industries 13 Economic Sectors
2nd 25 Industry Groups 20 Supersectors 32 Business Sectors
3rd 74 Industries 45 Sectors 61 Industry Groups
4th 163 Sub-Industries 173 Subsectors 153 Industries
Source: S&P Global/MSCI, FTSE Russell, Refinitiv

The following is an overview of each of the 3 major schemas and their corresponding structures:


The Global Industry Classification Standard (GICS) is a market-based classification system. According to GICS, as of March 2023, the classification system is comprised of over 58,000 trading securities across 125 countries, using the GICS, consisting of 11 sectors, 25 industry groups, 74 industries and 163 sub-industries. The first tier of the GICS structure divides the market into the following 11 sectors:

Energy Materials Industrials Consumer Discretionary Consumer Staples
Health Care Financials Information Technology Real Estate Communication Services Utilities
Source: S&P Global/MSCI

Each company classified in the system is assigned a GICS code at the sub-industry level, according to the firm's primary business activity.


The Industry Classification Benchmark (ICB) classifies more than 85,000 equity securities, in more than 80 countries, into 11 industries, 20 supersectors, 43 sectors, and 174 subsectors. The first tier of the ICB structure divides the market into the following 11 industries:

Energy Basic Materials Industrials Consumer Staples Health Care Real Estate
Consumer Discretionary Telecommunications Utilities Financials Technology
Source: FTSE Russell

The ICB allocates each company in the database to the subsector level that most closely represents the nature of its business, as determined by its source of revenue, or where it derives the majority of its income.


Developed in 2004, the Thomson Reuters Business Classification (TRBC) is an industry classification schema that includes over 72,000 companies from 130 countries. Unlike the other major classification systems, TRBC's classification system has 13 economic sectors, 32 business sectors, 61 industry groups, 153 industries, and 895 activities. The first tier of the TRBC structure divides the market into the following 13 economic sectors:

Basic Materials Consumer Cyclicals Energy Financials Health Care Industrials Institutions, Organizations & Associations
Academic & Educational Services Consumer Non-cyclicals Technology Utilities Real Estate Government Activity
Source: Refinitiv

Each company in the TRBC schema is assigned at the lowest level to an activity. The other levels of the schema are assigned according to a company's primary activity. When companies have multiple business segments, a company's primary activity is that which provides the largest revenue contribution.

Slight differences in methodologies

In many ways, the methodology used by the 3 main classification systems is more alike than different. However, there are subtle distinctions that can have a significant impact on the formation of sector funds and indexes, portfolio construction, and benchmarking. It may be beneficial for investors to be aware of these nuances in classification methodologies when trying to compare performance metrics across indexes, sectors, industries, and other sub-groupings.

If one excludes the 2 consumer-related sectors from each schema, the remaining 8 industries of the ICB seem to be an exact match to the remaining 8 sectors in GICS. However, the company groupings in each of these may also be considerably different.

The airlines provide another good example of how companies can be classified differently, depending on the methodology used. TRBC and GICS classify airlines as part of the Transportation subsector or industry, and to Industrials at the highest level, with other passenger transportation and delivery service firms. TRBC further segments companies at the lowest level, into those providing transportation or as those providing airline or airport services.

ICB, on the other hand, puts airlines into the Travel and Leisure industry. By putting airlines in the Travel and Leisure supersector with bars and restaurants, ICB creates a grouping that may have a much different sensitivity to the business cycle than the transportation group, as defined by TRBC or GICS.

Airline companies

Schema 1st Level 2nd Level 3rd Level 4th Level
TRBC Industrials Transportation Passenger Transportation Services Airlines
GICS Industrials Transportation Passenger Airlines N/A
ICB Consumer Discretionary Travel & Leisure Airlines N/A
Source: S&P Global/MSCI, FTSE Russell, Refinitiv
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Although in many cases the differences in these classifications systems may appear subtle, they can be significant for investors. This can be especially true for those that use sector-based assets or funds to invest with the business cycle.

For this reason, those investing using a sector-based strategy should understand how companies might be classified, and what the potential implications may be. This can be especially important when investing in funds that are designed to track certain sectors or industries, since the fund or index could be based on one of these various classification systems.

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Because of their narrow focus, investments in one sector tend to be more volatile than investments that diversify across many sectors and companies.

Past performance is no guarantee of future results.

Diversification does not ensure a profit or guarantee against loss.

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