This is a record of a lecture given by Mahes Visvalingam on Friday October 20, 2000  at IAP2000, the annual symposium of the UK Institution of Analysts & Programmers, which was held in association with the British Computer Society at Trinity House, London. 

The talk focused on the role of maps and diagrams in concept refinement and evaluation.  It illustrated their use in evaluating some summary statistics which inform elements of public policy.