With respect to an investment (e.g., a bond, stock, or fund share), market value is the cash value that selling such investment at a given price in the open market generates. As prices for investments tend to fluctuate daily, the actual or implied market value of an investment will likewise tend to fluctuate daily. With respect to a portfolio of securities, many custodians, trustees, and investment managers use independent pricing services to periodically value investment holdings and, therefore, in the aggregate, determine the market value of a portfolio.