Vanguard Total Stock Market Index Fund seeks to track the performance of the CRSP US Total Market Index that measures the investment return of the overall stock market. The fund employs an indexing investment approach designed to track the performance of the index, which represents approximately 100% of the investable U.S. stock market and includes large-, mid-, small-, and micro-cap stocks. It invests by sampling the index, meaning that it holds a broadly diversified collection of securities that, in the aggregate, approximates the full index in terms of key characteristics.