The HSI is the Hang Seng Index. It is the benchmark equity index in Hong Kong and is a capitalization weighted index of the 30 largest companies trading on the Hong Kong exchange. These 30 companies cover roughly 65% of the total market capitalization for the Hong Kong Exchange. The index has four subsectors – finance, industry, real estate investment trusts, and utilities. Because of the close ties between Hong Kong and mainland China there are many Chinese firms that are a part of the Hang Seng Index.