The proof of a good index is its value to the user.
The November/December 2000 issue of Key Words, the bulletin of the American Society for Indexing carried an article on usability testing, by Christine Nelsen Ryan and Sandra Henselmeier of Macmillan USA. The paper reports findings from a study conducted by the authors into readers’ use of indexes.
A summary of this report is in SIdelights Winter 2001, issue no. 4.
The Indexer October 2000, no. 2, contains the article by Susan C. Olason: “Let’s get usable! Usability studies for indexes” which discusses a series of studies from a systems engineering and human factors perspective.