The rates of assignment of narrower terms in the Thesaurus of ERIC Descriptors

Is there a link between the use of an indexing term and its physical similarity to its narrower terms? This analysis covered 1,296 entry terms, each with at least one narrower term in the ERIC Thesaurus. It measured the postings per document of the entry terms and their narrower terms. There was almost no correlation between how often a term is as signed and how many similar looking narrower terms it has. Nevertheless, there were some sets of narrower terms that had much higher postings per document rates than their entry terms. Many of these narrower terms were much newer to the Thesaurus than were their entry terms.