A measure of indexing consistency is developed based on the concept of 'fuzzy sets'. It assigns a higher consistency value if indexers agree on the more important terms than if they agree on less important terms. Measures of the quality of an indexer's work and exhaustivity of indexing are also proposed. Experimental data on indexing consistency are presented for certain categories of indexers, and consistency, quality, and exhaustivity values are compared and analyzed. The analysis of indexing exhaustivity leads to the conclusion that the increase of information as a result of group indexing is a process analogous to the Bradford's law of information scattering, Lotka's law of scientific productivity, and Zipf's law of vocabulary distribution. (Author)