Means for evaluation of the performance of an index fund performance. When the fund was established, it will choose the index as a reference index fund operations, and so on the basis of indicators for the addition and subtraction operations code, so fund managers to beat the index Trader is the goal; and for investors, this is for assess the merits of the performance of the fund operating as an objective criterion. Overseas funds because the underlying investments is quite extensive, so the reference index variety. In terms of Taiwan equity fund, for example, the commonly used reference index Taiwan Weighted Stock Index, and therefore how the performance of the fund, which is to rise and fall during the same period weighted stock price index (that is commonly known in the market) to make a comparison, and there are foreign funds due to exchange rate factors, it must be adjusted to the same currency.