A method and system for comparing and analyzing a first set of data with a second set of data received by a computer while maintaining a persistent key is disclosed. The method and system comprising the step of receiving a first data set and a second data set, each data set comprising at least one record, where each record reflects at least one of a plurality of entities. In this regard, more than one record may reflect the same entity (e.g., an entity representing a specific person). The method, program and system further comprises the step of utilizing an algorithm to compare the second data set to at least a portion of the first data set; identify or assign a persistent key (and perhaps the same persistent key for records reflecting the same entity) for each record in the second data set; and create a database or file (i.e., a journal).