Is used to measure the statistical value in financial markets or economic changes in the transaction, usually in the current period against the base period or before a percentage change is expressed, for example, the index of industrial production of the Federal Reserve Board in 1967 as the base period, base period index the 100. the index reached 121.7 in April 1973, which means that month industrial production increased compared with the base period by 22%. Index also often used to measure the volatility of trading stocks, futures, bonds and commodity markets, as well as to reflect market prices and surprising trend is the investor's investment decision as an important reference. The index is currently more famous: Dow Jones Industrial Average, the NYSE index, the American Stock Exchange index, the S & P five hundred kinds of stock index and the London Stock Exchange's Financial Times Industrial Index. Due to the rapid development of derivative financial products, to be used as the underlying stock index stock index futures and index option, becoming an important financial market traders speculative or hedging tool.