An index that measures the 12-month average of the monthly average yields (dealer bid rates) of 3-month certificates of deposit (CDs). The index is calculated by averaging the previous 12 rates of the 3-month CD rate. the yields are annualized based on the convention of a 360 day year. Central banks usually publish 3-month CD rates on a monthly basis. The certificates of deposit index (CODI), in the US, is published on or near the first Monday of each month. Because the CODI is an annual average, it is more stable than straight CD rates which demonstrate high volatility in response to changes in market rates.