Other non-derived variables such as issue date, maturity date, coupon rates, coupon payable dates, bank eligibility, tax status, and call status are obtained from the Treasury Department. All prices are checked for internal consistency, and secondary sources are used to check suspect prices. Considerable resources are expended in checking and improving the quality of the data. Errors are not common. Most of the errors which are found in checking the data are the result of the inaccuracy of the initial data source.
Some errors are coding errors.
Over time, coding errors are found and corrected. 1.1.4 Latest Changes and Additions Data error corrections are responsible for a small number of changes in the master file. No price edits were made. Treasury bills were located for gaps in the Fama Treasury Bill Term Structure Files. These are supplemented by a number of derived files developed by Professor Eugene Fama.