4. A method for assigning user codes (MR payer IDs) to prescription transaction data records fields selected from the group of a bank identification number (BIN) data field, and a Group ID (GID) data field and a data supplier specified payer indicia (DS) data field, and wherein a first subset of the data records have been previously assigned MR payer IDs based on known mappings of the values in their respective DS data fields, and a second subset of data records that have not been assigned MR payer IDs, the method comprising: for the first subset, extracting data records in which at least one of the BIN and GID fields are populated; determining the unique combinations of the BIN and GID values present in the first subset; determining the occurrence frequency of each unique combination of BIN and GID values in the first subset, selecting only those unique combinations of BIN and GID values that occur with a frequency greater than a cutoff limit X; for each such selected combination of BIN and GID values determining the frequency distribution of MR payer IDs assigned to corresponding data records in the first subset; selecting MR payer IDs having an occurrence frequency greater than a cutoff limit Y, for each such selected MR payer ID, establishing the combination of the BIN and GID values and the selected MR payer ID as a mapping rule for mapping data records in a second subset of data records.
4. A method for assigning user codes (MR payer IDs) to prescription transaction data records fields selected from the group of a bank identification number (BIN) data field, and a Group ID (GID) data field and a data supplier specified payer indicia (DS) data field, and wherein a first subset of the data records have been previously assigned MR payer IDs based on known mappings of the values in their respective DS data fields, and a second subset of data records that have not been assigned MR payer IDs, the method comprising: for the first subset, extracting data records in which at least one of the BIN and GID fields are populated; determining the unique combinations of the BIN and GID values present in the first subset; determining the occurrence frequency of each unique combination of BIN and GID values in the first subset, selecting only those unique combinations of BIN and GID values that occur with a frequency greater than a cutoff limit X; for each such selected combination of BIN and GID values determining the frequency distribution of MR payer IDs assigned to corresponding data records in the first subset; selecting MR payer IDs having an occurrence frequency greater than a cutoff limit Y, for each such selected MR payer ID, establishing the combination of the BIN and GID values and the selected MR payer ID as a mapping rule for mapping data records in a second subset of data records. 9. The method of claim 4 further comprising: for the second subset, grouping data records by unique combinations of BIN and GID values present in the second set; identifying unique BIN and GID combinations that do not have mapping rules established by analysis of the first subset of data records; manually verifying the MR payer ID for those data records that do not have matching rules established by analysis of the first subset of data records; establishing the unique combination of BIN and GID values and the corresponding manually verified MR payer ID as a mapping rule.