Launched on October 3rd, 2001, the Hang Seng Industry Classification System (HSICS) (previously named the Hang Seng Stock Classification System) is a comprehensive industry classification system designed for the Hong Kong stock market. Prompted by the listing of a wider variety of companies in different industries in Hong Kong, it meets the need for a detailed industry classification that reflects stock performance in different sectors. Covering 11 industries and 28 sectors, the two-tier HSICS caters for the unique characteristics of the Hong Kong stock market while maintaining international compatibility with mapping to international industry classification systems.
The primary parameter of stock classification is the sales revenue from each business area of a company. Profit or asset will also be taken into consideration where these better reflect the company's business.

A company will be assigned to a sector if the majority of its sales revenue (or profit or asset if relevant) is derived from that sector or its business fits most closely within that sector.

To preserve stability in the classification of a company, once a company is classified to a sector, it will remain there unless there is a significant change in how the company derives its revenue (or profit or asset if relevant).

The classification of each stock is based on audited financial information of the latest fiscal year contained in the company's annual report. Other publicly available information, such as prospectus, interim report or company announcements will be used if relevant.