The Tokyo Price Index (TOPIX) is a stock market index that is designed to measure the performance of all companies listed on the Tokyo Stock Exchange (TSE) First Section. It was first introduced in 1984 and is considered to be one of the most widely used stock market indexes in Japan.The TOPIX index is a capitalization-weighted index, which means that the weight of a particular stock in the index is determined by its market capitalization. The market capitalization is calculated by multiplying the number of shares outstanding by the current stock price. The higher the market capitalization of a stock, the greater its weight in the index.The TOPIX index is calculated based on the performance of all companies listed on the TSE First Section, regardless of their size or sector. This means that it includes large, blue-chip companies as well as small and mid-sized companies. The TOPIX index is calculated in real-time during the trading hours and it's considered as a benchmark index for the Japanese stock market.Investors can use the TOPIX index as a benchmark for the performance of the Japanese stock market, and it is also used as a benchmark for many exchange-traded funds (ETFs) and mutual funds that invest in Japanese stocks.In summary, The Tokyo Price Index (TOPIX) is a stock market index that measures the performance of all companies listed on the Tokyo Stock Exchange (TSE) First Section. It is a capitalization-weighted index that represents the performance of the Japanese stock market, and it is widely used as a benchmark index by investors, funds and analysts.