2. The CPI-U is the most widely followed and perhaps the most understood inflation index among alternative choices, such as the Gross Domestic Product (GDP) deflator and the Personal Consumption Expenditure (PCE) deflator. Monthly changes in the CPI-U represent the average changes in prices facing urban consumers with regard to a fixed basket of goods and services. This group of urban consumers represents about 87% of the total U.S. population. The Treasury reserves the right to substitute an alternative price index under the following circumstances: (1) the CPI-U is discontinued, (2) the CPI-U is altered materially to the detriment of the investor and/or the security, or (3) the CPI-U is altered by legislation or executive order in a manner harmful to the investor and/or the security.