Duration-based interest rate tables have the same format as for spot-style interest rate tables, but the durations are interpreted differently and the file name must end in the letters "_DUR.TXT" or "_dur.csv" (not case-sensitive).  With duration-based interest rates, there are typically two durations, such as 7% for the first 10 years and 4% thereafter.  In this case, all benefits payable after the end of the tenth year year are discounted to the tenth year at 4% and then, along with all benefits payable through the tenth year, discounted to the determination date at 7%.  This type of table is commonly used in Canada.