1. A computer implemented method comprising: a computer system identifying a target group of electronic customer records, each electronic customer record having data fields containing data pertaining to a customer; the computer system identifying a first focused blocker, the first focused blocker identifying a data value for an electronic customer record data field; the computer system analyzing the target group of electronic customer records to identify a first focused group of electronic customer records, the first focused group of electronic customer records comprising electronic customer records containing the first focused blocker data value; and the computer system comparing pairs of electronic customer records from the first focused group of electronic customer records to identify linked records, each linked record comprising two or more electronic customer records which pertain to a single customer entity.