This list of the 10 wealthiest people is a list of the world's 10 wealthiest people as of February 11, 2008, based on each person's total net worth. The total net worth is an estimate measured in United States dollars, based on the closing stock prices of the stock exchanges on which each person's company is listed, and exchange rates on February 11, 2008. Stock prices are defined as shares of ownership in a corporation, and exchange rates are defined as how much one currency is worth in terms of another. This list only represents each person's valuation on a single day due to daily fluctuations among exchange rates and stock valuations. The list does not include heads of state whose wealth is tied to their position (see list of heads of government and state by net worth).